Solution:
Show with the aid of a diagram how a wire is wound on a U-shaped piece of soft iron in order to make it an electromagnet. Complete the circuit diagram and label the poles of the electromagnet.
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Physics
(a) What name is given to a cylindrical coil of diameter less than its length?
(b) If a piece of soft iron is placed inside the coil mentioned in part (a) and current is passed in the coil from a battery, what name is then given to the device so obtained? (c) Give one use of...
The diagram in the figure shows a coil wound around a soft iron bar XY. (a) State the polarity at the end X and Y as the switch is pressed. (b)Suggest one way of increasing the strength of electromagnet so formed.
Solution - (a) At the ends, the polarity is as follows: X is for south pole.Y is for north pole.(b) Increasing the current flow in the coil is one technique to improve the electromagnet's...
You are required to make an electromagnet from a soft iron bar by using a cell, an insulated coil of copper and a switch. (a) Draw a circuit diagram to represent the process. (b) Label the poles of the electromagnet.
Solution:
Complete the following sentences:
(a) When current flows in a wire, it creates ____________ (b) On reserving the direction of current in a wire, the magnetic field produced by it gets _____. (C)A current carrying solenoid behaves...
How is the magnetic field due to a solenoid carrying current affected if a soft iron bar is introduced inside the solenoid?
Solution: When a soft iron bar is placed within the solenoid, the magnetic field increases. Explanation : The soft iron core aids in concentrating magnetic lines of force through the solenoid,...
What effect will there be on a magnetic compass when it is brought near a current-carrying solenoid?
Solution: Due to the solenoid at that point, the compass needle will rest in the direction of the magnetic field. Explanation : The Right hand thumb rule can readily determine the polarity of the...
Why does a current-carrying freely suspended solenoid rest along a particular direction? State the direction in which it rests.
Solution: At rest, a current-carrying freely suspended solenoid behaves similarly to a bar magnet. As a result, when a current-carrying solenoid is suspended freely. It sets itself in the same...
State two ways by which the magnetic field due to a current-carrying solenoid can be made stronger.
Solution: The magnetic field produced by a current-carrying solenoid can be amplified in several ways. (i) By increasing the number of turns in the solenoid's winding and(ii) By boosting the current...
The diagram shows a spiral coil wound on a hollow cardboard tube AB. A magnetic compass is placed close to it. Current is switched on by closing the key.
(a) What will be the polarity at the ends A and B? (b) How will the compass needle be affected? Give reason. (a) The north pole is at the end of A, and the south pole is at the end of B.(b) The...
The diagram in the figure shows a small magnet placed near a solenoid AB with its north pole N near the end A. Current is switched on in the solenoid by pressing the key K.
(a) State the polarity at the ends A and B. (b) Will the magnet be attracted or repelled? Give a reason for your answer. Solution: (a) The north pole is at the end A, and the south pole is at the...
Name and state the rule by which the polarity at the ends of a current carrying solenoid is determined.
Solution: The right hand thumb rule is the name of the rule. It asserts that if the current-carrying conductor is held in the right hand with the thumb pointing in the direction of current flow, the...
Draw a diagram to represent the magnetic field lines along the axis of a current-carrying solenoid. Mark arrows to show the direction of current in the solenoid and the direction of magnetic field lines.
Solution:
What is the direction of the magnetic field at the centre of a coil carrying current in
(i) the clockwise, (ii) the anticlockwise, direction? Solution: (i) The magnetic field in a clockwise direction is directed inwards along the coil's axis.(ii) The magnetic field in an anticlockwise...
A wire, bent into a circle, carries a current in an anticlockwise direction. What polarity does this face of the coil exhibit?
Solution: When a wire bent into a circle carries a current in an anticlockwise direction, the face of the coil exhibit north polarity.
Draw a labelled diagram showing the three magnetic field lines of a loop carrying current. Mark the direction of current and the direction of the magnetic field by arrows in your diagram.
Solution:
What will happen to a compass needle when the compass is placed below a wire with needle parallel to it and a current is made to flow through the wire? Give a reason to justify your answer.
Solution: The compass needle is deflected when a current is passed through a conductor wire. This creates a magnetic field surrounding it. As a result, the compass needle will deflect.
A straight wire lying in a horizontal plane carries a current from north to south.
(a) What will be the direction of the magnetic field at a point just underneath it? (b) Name the law used to arrive at this answer in part (a). Solution: (a) At a position immediately beneath the...
State a law, which determines the direction of the magnetic field around a current-carrying wire.
Solution: The right-hand thumb rule determines the direction of the magnetic field surrounding a current-carrying wire. It claims that if we hold the current-carrying conductor in our right hand...
How is the magnetic field due to a straight current-carrying wire affected if current in the wire is
(a) decreased, (b) reversed? Solution: (a) As the current is reduced, the magnetic field lines grow fewer. (b) When the direction of current is reversed, the magnetic field is reversed as...
Draw a diagram showing the direction of three magnetic field lines due to a straight wire carrying a current. Also show the direction of current in the wire.
Solution:
By using a compass needle describe how can you demonstrate that there is a magnetic field around a current-carrying conductor.
Solution: Experiment: A wire AB, running north-south, is linked to a battery through a rheostat and a tapping key in Figure. A compass needle is set just below the wire.Observations:(1) When the key...
At which point is the center of gravity situated in: (a) A triangular lamina and (b) A circular lamina?
(a) The centre of gravity of a triangular lamina is at the intersection of its medians. (b) The center of gravity of a circular lamina is at the center of the circular lamina
What is the position of the center of gravity of a: (a) rectangular lamina (b) cylinder?
(a) The point of intersection of a rectangular lamina's diagonals is where the lamina's center of gravity is located. (b) A cylinder's center of gravity is located at the midway of the cylinder's...
Is centrifugal force a real force?
Centrifugal force, on the other hand, is a made-up force.
Explain the motion of a planet around the sun in a circular path.
A planet orbits the sun in a circular path, with the sun's gravitational force providing the necessary centripetal force to allow the planet to move in a circular path.
What is centripetal force?
The centripetal force is the force acting on a body travelling in a circular path in the direction of the circular path's center.
Name the force required for circular motion. State its direction.
Circular motion necessitates the application of centripetal force. The direction of centripetal force is always in the direction of the circle's center.
A uniform circular motion is an accelerated motion. Explain it. State whether the acceleration is uniform or variable? Name the force responsible to cause this acceleration. What is the direction of force at any instant? Draw diagram in support of your answer.
When an object goes on a circular path at a constant speed, the amount of its velocity does not change; it just changes its direction. As a result, it's referred to as consistently accelerated motion.
State factor on which the position of the center of gravity of a body depend? Explain your answer with an example.
The center of gravity of a body with a certain mass position is determined by its form, or the distribution of mass. The center of gravity, for example, is found in the middle of a uniform wire....
Give one example of motion in which speed remains uniform, but the velocity changes.
The motion of a cyclist on a circular track is an example of motion in which the speed is constant but the velocity varies.
Is it possible to have an accelerated motion with a constant speed? Name such type of motion.
Yes, an accelerated motion with a constant speed is feasible. Uniform circular motion is an example of this type of motion.
Draw a neat labelled diagram for a particle moving in a circular path with a constant speed. In your diagram show the direction of velocity at any instant.
A particle moves in a circular route at a constant speed.
Can the center of gravity of a body be situated outside its material of the body? Give an example.
Yes, a body's centre of gravity can be located outside of the body's substance. A ring's center of gravity is an example.
Define the term ‘center of gravity of a body’.
The algebraic sum of moments of weights of particles composing the body is zero at the Centre of gravity of a body, and the total weight of the body is assumed to act at this location.
Explain the meaning of uniform circular motion. Why is such motion said to be accelerated?
When a particle moves at a constant speed in a circular path, it is said to be in a circular motion. The rotation of the Earth around the sun, for example, is an example of uniform circular motion.
A, B and C are the three forces each of magnitude 4N acting in the plane of the paper as shown in Figure. The point O lies in the same plane. (i) Name the forces producing (a) clockwise and (b) anticlockwise moments.
(i) (a) Clockwise moments are produced by vectors A and B. Explanation: Moment of force is called clockwise moment and it is negative if the turning impact on the body is clockwise. (b)...
A, B and C are the three forces each of magnitude 4N acting in the plane of the paper as shown in Figure. The point O lies in the same plane. (i) Which force has the least moment about O? Give a reason. (ii) Which force has the greatest moment about O? Give a reason.
(i) Moment of force= Force x Perpendicular distance, as we all know. Because the perpendicular distance between vector C and point O is the shortest, As a result, vector C will have the smallest...
200 g of ice at 0 °C converts into water at 0 °C in 1 minute when heat is supplied to it at a constant rate. In how much time, 200 g of water at 0 °C will change to 20 °C? Take specific latent heat of ice = 336 J g-1.
Solution: According to the question, mass of ice is mice= 200 g Time (t1) for ice to melt is 1 min, or 60 s Mass of water is mw = 200 g Temperature change of water is ΔT = 200 C Heat exchange occurs...
Complete the following sentences: (i) In a beam balance when the beam is balanced in a horizontal position, it is in ____________equilibrium. (ii) The moon revolving around the earth is in ____________ equilibrium.
(i) In beam balancing, the beam is in static equilibrium when it is balanced in a horizontal position. (ii) The moon is in dynamic balance as it revolves around the earth.
The amount of heat energy required to convert 1 kg of ice at -10oC completely into water at 100oC is 777000 J. calculate the specific latent heat of ice.
Specific heat capacity of ice = 2100 J kg-1 K-1, Specific heat capacity of water is 4200 J kg-1 K-1. Solution: According to the question, 1 kg of ice at -10oC is completely converted into water at...
Complete the following sentences:(i) The S.I. unit of moment of force is _________. (ii) In equilibrium algebraic sum of moments of all forces about the point of rotation is ______________.
(i) The Newton meter is the SI unit of moment of force. (Nm) (ii) The algebraic sum of moments of all forces around the point of rotation is zero in equilibrium.
Describe a simple experiment to verify the principle of moments, if you are supplied with a meter rule, a fulcrum and two springs with slotted weights.
Suspend a meter rule horizontally from a fixed support at point O using a strong thread. W1 and W2 now suspend two spring balances on either side of the thread with slotted weights. The meter rule...
State the principle of moments. Name one device based on it.
According to the principle of moments " the body is considered to be in equilibrium if the algebraic total of moments about the axis of rotation of all the forces operating on it is zero." A beam...
State two conditions for a body, acted upon by several forces to be in equilibrium.
The two conditions for a body to be in equilibrium are: (i)The resultant of all forces acting on a body must be zero, which is one of the two requirements for a body to be in equilibrium. (ii)All...
State the condition when a body is in (i) static, (ii) dynamic equilibrium. Give one example each of static and dynamic equilibrium.
(i) When the body remains in a condition of rest while being influenced by various forces, it is said to be in static equilibrium. Example: A book on a table is in a state of static equilibrium....
Calculate the total amount of heat energy required to convert 100 g of ice at -10o C completely into water at 100o C.
Specific heat capacity of ice = 2.1 J g-1 K-1, specific heat capacity of water = 4.2 J g-1 K-1, specific latent heat of fusion of ice = 336 J g-1. Solution: According to the question, 100 g of ice...
2 kg of ice melts when water at 100oC is poured in a hole drilled in a block of ice. What mass of water was used?
Given: Specific heat capacity of water = 4200 J kg-1 K-1, specific latent heat of ice = 336 × 103 J Kg-1. Solution: According to the question, 2 kg of ice melts when water at 100oC is...
What do you mean by equilibrium of a body?
A body is to be in equilibrium when a number of forces operating on it generate no change in its state of rest, linear, or rotational motion.
Prove that Moment of couple = Force x Couple arm.
Two equal and opposite forces, each of magnitude F, are applied at points A and B. The bar is rotated in an anticlockwise manner by the two forces. The coupling arm, or AB, is the perpendicular...
Define the moment of a couple. Write its S.I unit.
The product of both force and the perpendicular distance between the two forces equals the couple's moment. The S.I unit of moment of couple is Nm
What do you understand by the term couple? State its effect. Give two examples in our daily life where a couple is applied to turn a body.
A pair is formed by two equal and opposite parallel pressures that are not acting along the same line. The rotation must always be produced by a couple. Rotating a key in a lock and turning the...
Draw a neat labelled diagram to show the direction of two forces acting on a body to produce rotation in it. Also mark the point O about which the rotation takes place.
Two forces of magnitude F are applied at A and B, which are equal and opposite forces. The two forces rotate the bar in an anticlockwise direction, as seen in the diagram above.
A body is acted upon by two forces each of magnitude F, but in opposite directions. State the effect of the forces if (a)both forces act at the same point of the body. (b)the two forces act at two different points of the body at a separation r.
(a) The resultant force acting on the body = 0 $F-F\text{ }=\text{ }0$ (b) The forces tend to rotate the body between two forces about the midpoint. Moment of forces = $F\text{ }\times \text{ }r$...
A piece of ice of mass 40 g is added to 200 g of water at 50oC. Calculate the final temperature of the water when all the ice has melted. Specific heat capacity of water = 4200 J kg-1 K-1 and specific latent heat of fusion of ice =336 x 103 J kg-1.
Solution: According to the question, ice of mass 40 g is added to 200 g of water at 50oC. WE have to calculate the final temperature when all the ice has melted. Let this final temperature of the...
The adjacent diagram shows a heavy roller, with its axle at O, which is to be raised on a pavement XY. If there is friction between the roller and pavement, show by an arrow on the diagram the point of application and the direction of force to be applied.
Force F should be applied in the direction as shown in the above figure.
The stone of hand flour grinder is provided with a handle near its rim. Give a reason.
The stone of a hand flour grinder has a handle near its rim because it may be spun easily around the iron pivot at its center by applying modest force to the handle.
It is easier to turn the steering wheel of a large diameter than that of a small diameter. Give reason.
Turning a wide diameter steering wheel with a large distance from the centre of the rim requires less force. As a result, turning a large diameter steering wheel is easier than turning a small...
Find the result of mixing 10 g of ice at -10oC with 10 g of water at 10oC. Specific heat capacity of ice is 2.1 J g-1 K-1, specific latent heat of ice = 336 J g-1, and specific heat capacity of water = 4.2 J g-1 K-1.
Solution: According to the question, 10 g of ice at -10oC is mixed with 10 g of water at 10oC. And, heat capacity of ice = 2.1 J g-1 K-1, specific latent heat of ice = 336 J g-1, and specific heat...
A jackscrew is provided with a long arm. Explain why?
A jackscrew with a long arm that is used to hoist a heavy load, such as a vehicle, will require less effort to rotate in order to raise or lower the jack. As a result, the jackscrew's arm is quite...
A spanner (or wrench) has a long handle. Why?
The long handle of the spanner creates a bigger turning moment, making it easier to turn the nut with less force. As a result, the spanner's handle is quite long.
In an experiment, 17 g of ice is used to bring down the temperature of 40 g of water at 34oC to its freezing temperature. The specific heat capacity of water is 4.2 J g-1 K-1. Calculate the specific latent heat of ice. State one important assumption made in the above calculation.
Solution: According to the question Mass of ice (m1) is 17 g Mass of water m2 is 40 g Change in temperature is given by 34 – 0 = 34 K We know that the specific heat capacity of water is 4.2 J...
A refrigerator converts 100 g of water at 20oC to ice at -10oC in 73.5 min. calculate the average rate of heat extraction in watt. The specific heat capacity of water is 4.2 J g-1 K-1, specific latent heat of ice is 336 J g-1 and the specific heat capacity of ice is 2.1 J g-1 K-1.
Solution: According to the question, mass of water is 100g at 20 degrees C is converted to ice at -10 degrees C in 73.5 mins. We will first calculate the heat energy by using the following...
A molten metal of mass 150 g is kept at its melting point 800oC. When it is allowed to freeze at the same temperature, it gives out 75000 J of heat energy.
(a)What is the specific latent heat of the metal? (b) If the specific heat capacity of metal is 200 J kg-1 K-1, how much additional heat energy will the metal give out in cooling to – 50oC?...
How much heat energy is released when 5.0 g of water at 20o C changes into ice at 0o C? Take specific heat capacity of water =4.2 J g-1 K-1, specific latent heat of fusion of ice = 336 J g-1.
Solution: According to the question, mass of water m is 5.0 g Specific heat capacity (c) of water is 4.2 J g-1 K-1 Specific latent heat of fusion (L) of ice is 336 J g-1 In order to calculate the...
10 g of ice at 0oC absorbs 5460 J of heat energy to melt and change to water at 50oC. Calculate the specific latent heat of fusion of ice. Specific heat capacity of water is 4200 J kg-1 K-1.
Solution: According to the question, Mass of ice = 10 g = 0.01 kg Amount of absorbed heat energy is Q = 5460 J We have to find the specific latent heat of fusion of ice. We are given that the...
The specific latent heat of fusion of water is:
(a) 80 cal g-1 (b) 2260 J g-1 (c) 80 J g-1 (d) 336 J kg-1 Solution: The correct option is (a). The specific latent heat of fusion of water is 80 cal g-1
The S.I. unit of specific latent heat is:
(a) cal g-1 (b) cal g-1 K-1 (c) J kg-1 (d) J kg -1 K-1 Solution: The correct option is (c). The S.I. unit of specific latent heat is J kg-1
1 kg of ice at 0o is heated at a constant rate and its temperature is recorded after every 30 seconds till steam is formed at 100o C. Draw a temperature-time graph to represent the change of phases.
Solution: Temperature Time Graph
The diagram shows the change of phases of a substance on a temperature-time graph on heating the substance at a constant rate.
(a)What do parts AB, BC, CD and DE represent? (b) What is the melting point of the substance? (c) What is the boiling point of the substance? Solution: (a) The AB section depicts the solid's...
Explain the following:
(i) The surroundings become pleasantly warm when water in a lake starts freezing in cold countries. (ii) The heat supplied to a substance during its change of state, does not cause any rise in its...
Water in lakes and ponds do not freeze at once in cold countries. Give reason.
Solution: Ice has a sufficiently high specific latent heat of fusion of 336 J g-1. Before freezing, the water in lakes and ponds must release a considerable amount of heat into the atmosphere. The...
The temperature of surroundings starts falling when ice in a frozen lake starts melting. Give reasons.
Solution: The reason for this is that the heat energy needed to defrost the frozen lake is absorbed from the atmosphere. As a result, the temperature of the environment drops, and it becomes...
It is generally cold after a hail storm than during and before the hail storm. Give reasons.
Solution:...
The soft drink bottles are cooled by (i) ice cubes at 0°C, and (ii) iced-water at 0°C. Which will cool the drink quickly? Give reason.
Solution: To melt 1 g of ice into water at 0 C, it needs 336 J of heat energy from the drink. As a result, the bottle loses 336 J more heat energy to 1 g ice at 00 C than it does to 1 g ice-cold...
Ice cream appears colder to the mouth than water at 0oC. Give reasons.
Solution: Ice cream absorbs both heat energy and latent heat to reach room temperature, whereas water absorbs only heat energy. As a result, ice cream absorbs more energy from the tongue than water....
(a) Which requires more heat: 1 g ice at 0o C or 1 g water at 0oC to raise its temperature to 10oC? (b) Explain your answer in part (a).
Solution: (a) At 0 degrees Celsius, 1 g of ice requires extra heat because ice requires more heat energy equal to the latent heat of melting.(b) At 0 degrees Celsius, 1 g of ice absorbs 336 J of...
Which has more heat: 1 g of ice at 0o C or 1 g of water at 0oC? Give reasons.
Solution: At 0 degrees Celsius, 1 g of water has more heat than 1 g of ice. This is due to the fact that ice at 0°C absorbs 360 J of heat energy to convert to water at 0°C.
1 g ice at 0o C melts to form 1 g water at 0o. State whether the latent heat is absorbed or given out by ice.
Solution: 1 g ice at 0o C melts to form 1 g water at 0o. Because ice requires heat to melt, it will absorb heat in the form of latent heat and maintain a constant temperature until it melts.
‘The specific latent heat of fusion of ice is 336 J g-1 ‘. Explain the meaning of this statement.
Solution: The specific latent heat of fusion of ice is 336 J g-1. This implies that 1 g of ice at 00 C absorbs 336 J of heat energy in order to convert into water at 00 C.
Write the approximate value of specific latent heat of ice.
Solution: The approximate value of specific latent heat of ice is 336000 J kg-1
Define the term specific latent heat of fusion of ice. State its S.I. unit.
Solution: The thermal energy required to melt a unit amount of ice at 0 degrees C to water at 0 degrees C without changing the temperature is known as the specific latent heat of fusion of ice.
What do you understand by the term latent heat?
Solution: The latent heat is the heat energy absorbed or released during a phase shift that is not externally expressed as a rise or fall in temperature.
Complete the following sentences:
(a) Volume of ice …………. when it melts. (b)Decrease in pressure over ice ………….. its melting point. (c)Increase in pressure ………..the boiling point of water. (d)A pressure cooker is based on the...
It is difficult to cook vegetables on hills and mountains. Explains the reason.
Solution: At high altitudes, atmospheric pressure is low. As a result, the boiling point of water drops, and it is unable to give the necessary thermal energy to its contents for cooking. As a...
Write down the approximate range of temperature at which water boils in a pressure cooker.
Solution: The water boils at about 1200 C to 1250 C in a pressure cooker.
Water boils at 120 °C in a pressure cooker. Explain the reason
Solution: With increasing pressure, the boiling point of a liquid rises and falls with decreasing pressure. Pure water has a boiling point of 1000 degrees Celsius at one atmosphere of pressure....
What is the effect of increase in pressure on the boiling point of a liquid?
Solution: The boiling point of a liquid increases with the increase in pressure. Explanation - The energy required for the liquid molecules to expand to the gas phase increases as the pressure...
How is the boiling point of water affected when some salt is added to it?
Solution: When you add salt to water, it raises its boiling point. When ordinary salt is added to water, it boils at over 1000 degrees Celsius. Cooking becomes easier and faster as the salt in the...
How is the volume of water affected when it boils at 100oC?
Solution: When water boils at 100°C, its volume increases dramatically and its condition changes from liquid to steam. Although the temperature does not change during boiling, the volume expands due...
Explain the terms boiling and boiling point.
Solution: Boiling is the transition from a liquid to a gas phase due to the absorption of heat at a constant temperature.The boiling point of a liquid is defined as the temperature at which it...
State the effect of the increase of pressure on the melting point of ice.
Solution: The melting point of ice decreases as pressure increases. For every one atmosphere increase in pressure, the melting point of ice drops by 0.00720 C.
State the effect of the presence of impurity on the melting point of ice. Give one use of it.
Solution: When impurities are present in a substance, its melting point drops.This is used to make a freezing combination by combining salt with ice. Kulfis are made with the freezing mixture.
How does the (a) average kinetic energy (b) average potential energy of molecules of a substance change during its change in phase at a constant temperature, on heating?
Solution: (a) Molecules' average kinetic energy remains constant.(b) Molecules' average potential energy rises.Explanation: When a substance is heated to a constant temperature, i.e., during its...
A substance on heating undergoes (i) a rise in its temperature, (ii) A change in its phase without change in its temperature. In each case, state the change in energy of molecules of the substance.
Solution: (i) The average kinetic energy of molecules increases with the increase in temperature. (ii) Average potential energy of molecules increases with a change in its phase.
A substance changes from its solid state to the liquid state when heat is supplied to it
a. Name the process. b. What name is given to heat observed by the substance. c. How does the average kinetic energy of the molecules of the substance change. Solution: (a) This...
(a)What do you understand by the change of phase of substance?
(b)Is there any change in temperature during the change of phase? (c)Does the substance absorb or liberate any heat during the change of phase? (d) What is the name given to the energy absorbed...
1.0 kg of water is contained in a 1.25 kW kettle. Calculate the time taken for the temperature of water to rise from 25° C to its boiling point 100° C. Specific heat capacity of water = 4.2 J g-1 K-1.
Solution: We know that the Heat energy = Power × time Also we can write in the following manner - Heat energy = mc(change in temperature) Therefore, we can write => mc(change in temperature) = Power...
The temperature of 600 g of cold water rises by 15o C when 300 g of hot water at 50o C is added to it. What was the initial temperature of the cold water?
Solution: According to the question, Mass of hot water (m1) is 300 g Temperature (T1) is 500 C Mass of cold water (m2) is 600 g Change in the temperature of cold water (T – T2) is 150 C Let the...
200 g of hot water at 80o C is added to 300 g of cold water at 10oC. Neglecting the heat taken by the container, calculate the final temperature of the mixture of water. Specific heat capacity of water = 4200 J kg-1 K-1.
Solution: According to the question, Mass of hot water (m1) is 200 g Temperature of hot water (T1) is 800 C Mass of cold water (m2) is 300 g Temperature of cold water (T2) is 100 C We have to find...
45 g of water at 50o C in a beaker is cooled when 50 g of copper at 18oC is added to it. The contents are stirred till a final constant temperature is reached. Calculate the final temperature. The specific heat capacity of copper is 0.39 J g-1 K-1 and that of water is 4.2 J g-1 K-1. State the assumptions used.
Solution: According to the question, Mass of water (m1) is 45 g Temperature of water (T1) is 500 C Mass of copper (m2) is 50 g Temperature of copper (T2) is 180 C We have to find the final...
A mass of 50 g of a certain metal at 150° C is immersed in 100 g of water at 11° C. The final temperature is 20° C. Calculate the specific heat capacity of the metal. Assume that the specific heat capacity of water is 4.2 J g-1 K-1.
Solution: According to the statement, mass of the metal is 50g and the change in temperature is equal to (150 – 20) Then using the expression for heat energy, we have - Heat lost by metal = m × s ×...
0.5 kg of lemon squash at 30o C is placed in a refrigerator which can remove heat at an average rate of 30 J s-1. How long will it take to cool the lemon squash to 5o C? Specific heat capacity of squash = 4200 J kg-1 K-1.
Solution: According to the question, Change in temperature = 30 – 5 = 25 K We know that the expression for heat energy is => △Q = mc△T Substituting values, we get △Q = 0.5 × 4200 × 25 = 52500 J Heat...
An electric heater of power 600 W raises the temperature of 4.0 kg of a liquid from 10.0 0C to 15.0 0C in 100 s. Calculate:
(i) the heat capacity of 4.0 kg of liquid, and (ii) the specific heat capacity of liquid Solution: According to the statement, Power (P) of heater is 600 W Mass (m) of liquid is 4.0 kg Change in...
Find the time taken by a 500 W heater to raise the temperature of 50 kg of material of specific heat capacity 960 J kg-1 K-1, from 18oC to 38oC. Assume that all the heat energy supplied by heater is given to the material.
Solution: According to the question, we have - Specific heat capacity (c) of the material is 960 J kg-1 K-1 Change in temperature becomes △T = (38 – 18)0 C = 200 C or, △T = 20 K (temperature...
1300 J of heat energy is supplied to raise the temperature of 0.5 kg of lead from 20oC to 40oC. Calculate the specific heat capacity of lead.
Solution: According to the question, Heat energy supplied is 1300 J and the mass of lead is 0.5 kg Also the change in temperature is (40 – 20)0 C = 200 C Expression for specific heat capacity of...
Calculate the amount of heat energy required to raise the temperature of 100 g of copper from 20oC to 70oC. Specific heat of capacity of copper =390 J kg-1 K-1.
Solution: According to the question, Mass of copper m is 100 g = 0.1 kg Change of temperature is △t = (70 – 20)0 C = 500 C Also the specific heat capacity of copper is 390 J kg-1 K-1 Expression for...
A piece of iron of mass 2.0 kg has a heat capacity of 966 J K-1. Find
(i) Heat energy needed to warm it by 15oC, and (ii) Its specific heat capacity in S.I unit. Solution: (i) We know that the heat energy required is given by the product of heat capacity and...
(a)Calculate the heat capacity of a copper vessel of mass 150 g if the specific heat capacity of copper is 410 J kg-1 K-1.
(b)How much heat energy will be required to increase the temperature of the vessel in part (a) from 25oC to 35oC? Solution: (a) According to the question, Mass of copper vessel is 150 g, or 0.15 kg...
By imparting heat to a body, its temperature rises by 150C. What is the corresponding rise in temperature on the Kelvin scale?
Solution: One degree on the Kelvin scale is the same size as one degree on the Celsius scale. As a result, the temperature difference or change is the same on both the Kelvin and Celsius scales. As...
The specific heat capacity of water is:
(a) 4200 J kg-1 K-1 (b) 420 J g-1 K-1 (c) 0.42 J g-1 K-1 (d) 4.2 J kg-1 K-1 Solution: The correct option is (a). The specific heat capacity of water is 4200 J...
The S.I. unit of specific heat capacity is:
(a) J kg-1 (b) J K-1 (c) J kg-1 K-1 (d) kcal kg-10C-1 Solution: The correct option is (c). The S.I. unit of specific heat capacity is J kg-1 K-1
The S.I. unit of heat capacity is:
(a) J kg-1 (b) J K-1 (c) J kg-1 K-1 (d) cal 0C-1 Solution: The correct option is (b). The S.I. unit of heat capacity is J K-1.
Why the base of a cooking pan made thick and heavy?
Solution: The base of a cooking pan is thick and heavy because it has a large heat capacity, which allows it to heat up slowly and impart sufficient heat energy to the food for proper cooking. It...
(a) What is calorimeter?
(b)Name the material of which it is made of. Give two reasons for using the material stated by you. (c) Out of the three metals A, B and C of specific heat 900 J kg-1 °C-1, 380 J...
A liquid X has specific heat capacity higher than the liquid Y. Which liquid is useful as (i) coolant in car radiators and, (ii) heat reservoir to keep juice bottles without freezing?
Solution: Because liquid X has a higher specific heat capacity than liquid Y, the temperature rise for X will be smaller than for Y for the same mass and heat energy. (i) As a coolant in automotive...
Give one example each where high specific heat capacity of water is used (i) as coolant, (ii) as heat reservoir.
Solution: (i) Water is used as a coolant in automotive radiators and generators. (ii) To prevent wine and juice bottles from freezing, water is employed as a heat reservoir.
What property of water makes it an effective coolant?
Solution: The heat energy from heated sections of a machine is eliminated by allowing water to flow in pipes surrounding them. Because of its high specific heat capacity, water in pipes may extract...
Water is used in hot water bottles for fomentation. Give reason.
Solution:...
Discuss the role of high specific heat capacity of water with reference to climate in coastal areas.
Solution: Water has an extremely high specific heat capacity, around five times that of sand. As a result, the heat energy required to raise the temperature by a given mass of water is roughly five...
Why do the farmers fill their fields with water on a cold winter night?
Solution: If the air temperature drops below 0 C on a cold winter night, water in the fine capillaries of plants freezes. It causes the veins to burst due to the increase in volume of water caused...
A mass m1 of a substance of specific heat capacity c1 at temperature T1 is mixed with a mass m2 of other substance of specific heat capacity c2 at a lower temperature T2. Deduce the expression for the temperature t of the mixture. State the assumption made, if any.
Solution: According to the statement, a mass m1 of a substance A having specific heat capacity c1 at temperature T1 is mixed with a mass m2 of other substance B having specific heat capacity c2 at a...
What is the principle of the method of mixture? What other name is given to it? Name the law on which this principle is based.
Solution: The amount of heat energy lost by the hot body is equal to the amount of heat energy absorbed by the cool body. This is known as the principle of the method of mixture. The principle of...
Two blocks P and Q of different metals having their mass in the ratio 2:1 are given the same amount of heat. Their temperatures rise by the same amount, compare their specific heat capacities.
Solution: Let Cp and Cq denote the specific heat capacities of blocks P and Q respectively According to the question, the mass ratio of P and Q is 2:1. Therefore, if mass of Q is m then the mass of...
Same amount of heat is supplied to two liquids A and B. The liquid A shows a greater rise in temperature. What can you say about the heat capacity of A as compared to that of B?
Solution: The temperature rises quickly and dramatically when a substance has a low specific heat capacity. As a result, liquid A has a lower heat capacity than liquid B.
Write the expression for the heat energy Q received by m kg of a substance of specific heat capacity c J kg-1 K-1 when it is heated through △ to C.
Solution:...
Name three factors on which the heat energy absorbed by a body depends and state how does it depend on them.
Solution: The heat energy absorbed by a body is determined by three parameters. (i) Body mass: The amount of heat energy required is directly proportional to the object's mass. (ii) Increase in body...
Name the factors on which the heat energy liberated by a body on cooling depends.
Solution: Such factors on which the heat energy liberated by a body upon cooling depends are as follows: (i) Mass of that body (ii) Specific heat capacity of that body (iii) Temperature of that...
Specific heat capacity of a substance A is 3.8 J g-1 K-1 and of substance B is 0.4 J g-1 k-1. Which substance is a good conductor of heat? How did you arrive at your conclusion?
Solution: Substance B has a lower specific heat capacity than substance A. As a result, given the same mass and heat energy, B's temperature rise will be greater than A's. The lower a substance's...
What do you mean by the following statements:
(i) The heat capacity of a body is 50 JK-1? (ii) The specific heat capacity of copper is 0.4 J g-1 K-1? Solution: (i) According to the statement, the heat capacity of a body is 50 JK-. This...
Write the approximate value of specific heat capacity of water in S.I. unit.
Solution: The specific heat capacity of water is approximately 4200 J kg-1 K-1. Water is the liquid with the highest specific heat capacity. The amount of heat that one gram of a substance needs...
Name a liquid which has the highest specific heat capacity.
Solution: Water has the highest specific heat capacity. Explanation : The high heat capacity of water is due to hydrogen bonding between water molecules. Hydrogen bonds are destroyed when heat is...
State three differences between the heat capacity and specific heat capacity.
Solution: Heat Capacity (a) The quantity of heat energy necessary to elevate the temperature of the entire body by 10 degrees Celsius is known as heat capacity.(b) It is determined by the body's...
How is the heat capacity of a body related to the specific heat capacity of its substance?
Solution: The equation that links a body's heat capacity to its substance's specific heat capacity is Mass x Heat Capacity = Specific Heat Capacity
Define the term specific heat capacity and state its S.I. unit.
Solution: The amount of heat energy essential to raise the temperature of a unit mass of a substance by 10C (or 1 K) is known as the specific heat capacity of that substance. Joule per kilogram per...
Define the term heat capacity and state its S.I. unit.
Solution: The amount of heat energy required to raise its temperature by 10C or 1 K is termed as the heat capacity of a body. The S.I. unit of heat capacity is joule per kelvin (JK-1).
Define calorimetry.
Solution: Calorimetry is the measurement of the quantity of heat.
State three differences between heat and temperature.
Solution - Heat Heat is a type of internal energy created when molecules in a substance move randomly and attract each other.The joule is the SI unit of heat (J).The principle of calorimetry is used...
Define temperature and name its S.I. unit.
Solution: When two bodies of differing temperatures come into contact. Then the temperature is the quantity which dictates the direction of heat flow. Kelvin is the SI unit of temperature (K).
Define one kilo-calorie of heat.
Solution: The heat energy essential to raise the temperature of 1 kg of water from 14.50 C to 15.50 C is known as One kilo-calorie.
Define the term calorie. How is it related to joule?
Solution: The thermal energy required to increase the temperature of 1 g of water from 14.50 C to 15.50 C is equal to one calorie. The S.I. unit joule is related to the calorie in the following way:...
Name the S.I. unit of heat.
Solution: Heat is defined as the internal energy of the molecules that make up the body. When two bodies are kept in contact, it flows from the hot one to the cold one. Joule is the S.I. unit of...
Define the term heat.
Solutions: Heat is defined as the internal energy of the molecules that make up the body. When two bodies are kept in contact, it flows from the hot one to the cold one.
State the changes in the position, size and nature of the image When the object is brought from infinity up to a concave lens. Illustrate your answer by drawing diagrams.
Solution: (i) When an object (AB) is located at infinity, parallel rays from the object appear to fall on the concave lens. It causes an image to form at focus. The scale of this image is greatly...
State the changes in the position, size and nature of the image when the object is brought from infinity up to the convex lens. Illustrate your answer by drawing the ray diagrams.
Solution: (i) When the object is situated at infinity, the position of the image is at F2. It is real, inverted and very much diminished in size. (ii) When the object (AB) is situated beyond 2F1,...
Complete the following table:
Type of lensPosition of objectNature of imageSize of imageConvexBetween the optical centre and focusConvexAt focusConcaveAt infinityConcaveAt any distance Solution: Type of lensPosition of...
In each of the following cases, where must an object be placed in front of a convex lens so that the image formed is
(c)inverted and enlarged, (d)upright and enlarged? Solution: (c) Between F and 2F Object must be placed between F and 2F of a convex lens so that the image formed is inverted and enlarged. (d)...
In each of the following cases, where must an object be placed in front of a convex lens so that the image formed is
(a)at infinity, (b)of same size as the object, Solution: (a) At focus, Object must be placed at the focus of a convex lens so that the image is formed at infinity. (b) At 2F, Object must be placed...
Give two characteristics of the virtual image formed by a convex lens.
Solution: The virtual image formed by a convex lens will always be i) erect and ii) magnified.
Give two characteristics of the image formed by a concave lens.
Solution: The image formed by a concave lens is virtual and diminished.
Can a concave lens form an image of size two times that of the object? Give reason?
Solution: No, a concave lens cannot produce a picture two times the size of the item because it diverges the incident rays, resulting in a decreased image.
(a)Name the lens which always forms an erect and virtual image.
(b)State whether the image in part (a) is magnified or diminished? Solution: (a) Since lens here always forms an erect and virtual image, the lens used here is a concave lens (b) The image formed by...
A lens forms an upright and magnified image of an object.
(a)Name the lens. (b)Draw a labelled ray diagram to show the image formation. Solution: (a) Since lens forms an upright and magnified image of an object, the lens used here is a convex lens....
A lens forms an inverted image of an object.
(a) Name the kind of lens. (b) State the nature of the image whether real or virtual? Solution: (a) Since the lens forms an inverted image of an object, it is a convex lens. (b) The image...
Draw a ray diagram to show how a converging lens can form an image of the sun. Hence give a reason for the term ‘burning glass’ for a converging lens used in this manner.
Solution: Because the Sun is at infinity, the convex lens creates an image at the second focus point that is both real and greatly reduced in size. The sun's beams converge at the focus of the lens,...
Draw a ray diagram to show how a converging lens is used as a magnifying glass to observe a small object. Mark on your diagram the foci of the lens and the position of the eye.
Solution: The object is positioned between the focal point F1 and the convex lens, and its image is generated on the same enlarged side of the lens. As a result, this lens can be used as a...
A lens forms an upright and diminished image of an object placed at its focal point. Name the lens and draw a ray diagram to show the formation of an image.
Solution: The image of an object placed at the focal point of a concave lens is vertical and diminished.
Draw a ray diagram to show how a converging lens can form a real and enlarged image of an object.
Solution: The above figure shows the image formed is i) real, ii) enlarged and iii) inverted.
Show by a ray diagram that a diverging lens cannot form a real image of an object placed anywhere on its principal axis.
Solution: This ray diagram shows that a diverging lens cannot form a real image of an object placed anywhere on its principal axis.
Classify as real or virtual, the image of a candle flame formed on a screen by a convex lens. Draw a ray diagram to illustrate how the image is formed.
Solution: Suppose that the object is placed beyond 2F1 and its diminished image is formed between F2 and 2F2. Such an image is real and inverted. Here the object is AB and the image is real and...
A lens always forms an image between the object and the lens. (a) name the lens. (b) Draw a ray diagram to shown the formation of such an image. (c) state three characteristics of the image.
Solution: (a) Concave lens is a lens that forms the image between the object and itself. (b) This figure shows the ray diagram (c) The three characteristics of the image are (i) virtual, (ii) erect...
A lens forms an erect, magnified and virtual image of an object.
(a) Name the kind of lens. (b) Where is the object placed in relation to the lens? (c) Draw a ray diagram to show the formation of the image. (d) Name the device which uses this principle. Solution:...
A convex lens forms an image of an object equal to the size of the object. (a) Where is the object placed in front of the lens? (b) Draw a diagram to illustrate it. (c) State two more characteristics of the image.
Solution: (a) The object is placed at a distance equal to twice the focal length of the lens. (b) (c) The image formed is real and inverted
A converging lens forms the image of an object placed in front of it, beyond 2F2 of the lens.
(a) Where is the object placed? (b) Draw a ray diagram to show the formation of an image. (c) State its three characteristics of the image. Solution: (a) Since the image of an object formed by a...
The diagram given below in fig. shows the position of an object OA in relation to a converging lens L whose foci are at F1 and F2.
(i) Draw two rays to locate the position of the image. (ii) State the position of the image with reference to the lens. (iii) Describe the three characteristics of the image. (iv) Describe how the...
The following diagram in Fig. shows an object AB and a converging lens L with foci F1 and F2.
(a) Draw two rays from the object AB and complete the diagram to locate the position of the image CD. Also mark on the diagram the position of eye from where the image can be viewed. (b) State...
Study the diagram below.
(i)Name the lens LL’. (ii)What are the points O and O’ called? (iii)Complete the diagram to form the image of the object AB. (iv)State three characteristics of the image. Solution: (i) LL’...
Study the diagram given below.
(a) Name the lens LL’. (b) What are the points O and O’ called? (c) Complete the diagram to form the image of the object AB. (d) State the three characteristics of the image. ...
Distinguish between a real and a virtual image.
Solution: Real Image (i) The actual junction of the rays refracted by the lens produces a real image.(ii) On a screen, a real image can be obtained.(iii) In relation to the object, a real image is...
Where must a point source of light be placed in front of a convex lens so as to obtain a parallel beam of light?
Solution: When a source of light is placed at the first focal point, which is the focal point to the left of the optical centre of the convex lens, the rays of light refracted through the convex...
In the diagrams below, XX’ represents the principal axis, O the optical centre and F the focus of the lens. Complete the path of the rays A and B as they emerge out of the lens.
Solution -
What are the three principal rays that are drawn to construct the ray diagram for the image formed by a lens? Draw diagram to support your answer.
Solution: (i) A ray of light incident at the lens' optical centre O goes through the lens without deviating. (ii) After refraction, a ray of light incident parallel to the primary axis of the lens...
Complete the following sentence
(a)An object is placed at a distance of more than 40 cm from a convex lens of focal length 20 cm. The image formed is real, inverted and……………. (b)An object is placed at a distance 2f from a convex...
Two sounds A and B are of same amplitudes, same waveforms but of frequencies f and 2f respectively. Then:
(a) B differ in quality from A
(b) B is grave, A is shrill
(c) B is shrill, A is grave
(d) B is louder than A
Two sounds, A and B, have the same amplitudes and waveforms but have different frequencies of f and 2f. Then B becomes strident, and A becomes solemn.
Two sounds of same loudness and same pitch produced by the two different instruments differ in their
(a) amplitudes
(b) frequencies
(c) waveforms
(d) all the above
The waveforms of two sounds of the same loudness and pitch generated by two different instruments differ.
By reducing the amplitude of the sound wave, its:
(a) pitch increases
(b) loudness decreases
(c) loudness increases
(d) pitch decreases
The loudness of a sound wave falls when its amplitude is lowered.
State one difference between a musical note and a noise.
Music is regular, smooth, and enjoyable to listen to.Noise is abrasive, dissonant, and unpleasant to listen to.The volume of the music is low (between 10 dB to 30 dB)The volume ...
In what respect does the wave pattern of a noise and music differ? Draw diagram to explain your answer.
A noise's wave pattern is irregular, whereas music's wave pattern is regular. The waveforms of music and noise are depicted in the diagram below.
Find the position and magnification of the image of an object placed at distance of 8.0 cm in front of a convex lens of focal length 10.0 cm. Is the image erect or inverted?
Solution: According to the question, Object distance is u = – 8 cm Focal length is f = 10 cm We have to find out the image distance v The expression of the Len’s formula is 1 / f = 1 / v – 1 / u...
A microphone is connected to the Y-input of a C.R.O. Three different sounds are made in turn in front of the microphone. Their traces (a), (b) and (c) produced on the screen are shown in figure
(i) Which trace is due to the loudest sound? Give the reason for your answer.
(ii) Which trace is due to the sound with the lowest pitch? Explain your answer.
(i) Because the loudest sound has the highest amplitude, Figure (b) is attributable to it. (ii) Because frequency is the lowest, figure (a) is due to the sound with the lowest pitch.
A concave lens is a focal length of 30 cm. Find the position and magnification (m) of image for an object placed in front of it at distance 30 cm. State whether the image is real on virtual?
Solution: According to the question Object distance is u = -30 cm Focal length is f = -30 cm We have to find out the image distance v According to the Len’s formula, we have - 1 / f = 1 / v – 1 / u...
Shows the wave patterns of three sounds A, B and C. Name the characteristic of sound which is same between (i) A and B, (ii) B and C, and (iii) C and A
(i)The amplitude and waveform of A and B are identical. As a result, both the volume and the quality are the same. (ii) The amplitude and waveform in figures B and C are not the same. As a result,...
The sketches I to IV in figure show sound waves, all formed in the same time interval.
Which diagram shows
(i) a note from a musical instrument,
(ii) a soft (or feeble) note,
(iii) a bass (or low frequency) note.
(i)A musical instrument note is depicted in Figure IV. (ii) A faint (or feeble) note is shown in Figure I. (iii) A bass (or low frequency) note is shown in Figure 2.
Name the characteristic of the sound affected due to a large in its (i) amplitude, (ii) waveform, and (iii) frequency
(i) Loudness is a property of a sound that is impacted by a big amplitude. (ii) Quality is a property of a sound that has been altered by a large in its waveform. (iii) Pitch is a property of sound...
State the factor that determines
(i) the pitch of a note,
(ii) the loudness of the sound heard, and
ii) the quality of the note.
(i)The pitch of a note is determined by its frequency. (ii) The loudness of a sound is determined by its amplitude. (iii) Waveforms define the note's quality.
The magnification by a lens is +0.5. Name the lens and state how are u and v related?
Solution: The concave lens' image is always imaginary, upright, and smaller than the object. As a result, the magnification is always positive and smaller than a factor of one. The relationship...
Which characteristic of sound makes it possible to recognize a person by his voice without seeing him?
The timbre, or quality, of a sound is the feature that allows us to recognize a person by his voice even when we are unable to see him.
The magnification by a lens is -3. Name the lens and state how are u and v related?
Solution: The image is real and inverted, as indicated by the negative magnification value. The magnification is larger than 1, implying that the image is magnified. As a result, the lens should be...
Two musical notes of the same pitch and same loudness are played on two different instruments. Their wave patterns are as shown in the diagram below. Explain why the wave patterns are different.
Subsidiary notes are produced by many instruments. A note played on one instrument has many subsidiary notes, but a note played on another instrument has only a few subsidiary notes. As a result,...
Two identical guitars are played by two persons to give notes of the same loudness and pitch. Will they differ in quality? Give a reason for your answer
Because the guitars are same, their waveforms will be comparable, and so their quality will be similar.
The power of a lens is -2.0 D. Find its focal length and its kind.
Solution: According to the question - The power of a lens is -2.0 D We know that the expression of Power of a lens is P = 1 / f Upon substituting values, we have => -2 = 1 / f Or, f = 1 / -2 = -0.5...
How does the two sounds of the same loudness and same pitch produced by different instruments differ? Draw diagrams to illustrate your answer.
Because of their varied waveforms, two sounds of the same loudness and pitch generated by different instruments sound different. Along with the main note, the waveforms are determined by the number...
Name the characteristic which enables one to distinguish the sound of two musical instruments even if they are of the same pitch and same loudness.
The quality or timbre of the sound is the feature that allows one to identify the sound of two musical instruments even if they are of the same pitch and volume.
The diagram below shows three different modes of vibration P, Q and R of the same string of a givens length.
(a) Which vibration will produce a louder sound and why?
(b) Which vibration will produce sound of maximum shrillness (or pitch) and why?
(c) What is the ratio of the wavelength of vibrations P and R?
(a) R has the greatest amplitude. As a result, R will make a louder sound. (b) P has the highest frequency. As a result, P will generate the most shrillness. (c) The wavelength ratio of the...
Complete the following sentences:
(a)The pitch of sound increases, if its frequency ___________.
(b)If the amplitude of the sound is halved, its intensity becomes __________.
(a) As the frequency of a sound increases, so does its pitch. (b) If the sound's amplitude is half, the intensity is reduced by one-fourth.
The frequencies of notes given by flute, guitar and trumpet are respectively 400 Hz, 200 Hz and 500 Hz. Which one of these has the highest pitch?
The trumpet has the highest frequency. The trumpet, therefore, has the greatest pitch.
How is it possible to detect the filling of a bottle under a water tap by hearing the sound at a distance?
As the water level in a bottle held under a water faucet rises, the length of the air column reduces. As a result, the frequency of sound generated rises. As a result, hearing sound from a distance...
Draw a diagram to show the wave pattern of high pitch note and a low pitch note, but of the same loudness.
The diagram for a high-pitched note is as follows: The diagram for a low-pitched note is as follows:
The focal length of a convex lens is 25 cm. Express its power with sign.
Solution: According to the question, Focal length is f = +25 cm = +0.25 m We know that the expression of power of a lens is - P = 1 / f Substituting value of focal length, we get => P = 1 / +0.25...
Name and define the characteristic which enables one to distinguish two sounds of same loudness, but of different frequencies given by the same instrument.
Pitch is the feature that distinguishes two sounds of equal volume but different frequency produced by the same instrument.