When the magnetic field is lowered in t, the magnetic flux across the conducting ring drops to zero from its maximum. E2b = induced emf According to Faraday's law of emf, The induced emf is equal to...
A rectangular loop of wire ABCD is kept close to an infinitely long wire carrying a current II ( ) t = o (1– /t T ) for 0 ≤ ≤ t T and I (0) = 0 for t > T. Find the total charge passing through a given point in the loop, in time T. The resistance of the loop is R.
If the instantaneous current is t, then I(t) = 1/R d/dt I(t) If q is the charge that passes during time t, dQ/dt = I(t) 1/R d/dt = dQ/dt When we integrate the equation, we obtain Q = 0L1L2/2R log...
Consider an infinitely long wire carrying a current I (t ), with dI dt =λ= constant. Find the current produced in the rectangular loop of wire ABCD if its resistance is R.
The strip has a width of dr and a length of l, and it is located inside the rectangular box at a distance of r from the current-carrying conductor's surface. The magnetic field along the length of...
i) When the position of the rotating conductor is assumed to be at the time interval t = 0 to t = π/4ꞷ We get current I = 1/2 Bl2ꞷ/λl sec2 ꞷt cos ꞷt = Blꞷ/2λ cos ꞷt ii) When the position of the rotating conductor is at time interval π/4ꞷ < t < 3π/4ꞷ We get current I = 1/2 Blꞷ/λ sin ꞷt iii) When the position of the rotating conductor is at time interval 3π/4ꞷ < t < π/ꞷ We get current I = 1/2 Blꞷ/ λ sin ꞷt
I If the spinning conductor's location is considered to be in the time period t = 0 to t = 4 We obtain current I = 1/2 Bl2/l sec2 t cos t = Bl/2 cos t = Bl/2 cos t = Bl/2 cos t = Bl/2 cos t = Bl/2...
A conducting wire XY of mass m and negligible resistance slides smoothly on two parallel conducting wires. The closed-circuit has a resistance R due to AC. AB and CD are perfect conductors. There is a magnetic field B = B t(k ). (i) Write down the equation for the acceleration of the wire XY. (ii) If B is independent of time, obtain v(t) , assuming v (0) = u0. (iii) For (b), show that the decrease in kinetic energy of XY equals the heat lost in R.
m = B.A = BA cos m The area vector is A, while the magnetic field vector is B. e1 = -dB(t)/dt lx e1 e2 = B(t) lv (t) The total emf in the circuit is equal to the emf owing to field change plus the...
A magnetic field B = Bo sin ωt k covers a large region where a wire AB slides smoothly over two parallel conductors separated by a distance d. The wires are in the x-y plane. The wire AB (of length d) has resistance R and the parallel wires have negligible resistance. If AB is moving with velocity v, what is the current in the circuit? What is the force needed to keep the wire moving at constant velocity?
Allow wire AB to travel with velocity v at time t = 0. x(t) = vt at time t AB = e1 = Blv Motional emf across (Bo sin t)vd = e1 (-j) d(B)/dt = e2 e2 = -B0 cos tx (t)d e2 = -B0 cos tx (t)d e2 = -B0...
There are two coils A and B separated by some distance. If a current of 2 A flows through A, a magnetic flux of 10-2 Wb passes through B (no current through B). If no current passes through A and a current of 1 A passes through B, what is the flux through A?
The current flowing through the coil is denoted by Ia. Mutual induction between A and B is known as Mab. The number of turns in coil A is Na. The number of turns in coil B is Nb. an is the flux...
A (current vs time) graph of the current passing through a solenoid is shown in Fig 6.9. For which time is the back electromotive force (u) a maximum. If the back emf at t = 3s is e, find the back emf at t = 7 s, 15s and 40s. OA, AB and BC are straight line segments.
We may deduce from the graph that when the rate of change of magnetic flux reaches its highest, the electromagnetic force, which is proportional to the rate of change of current, reaches its...
Find the current in the wire for the configuration. Wire PQ has negligible resistance. B, the magnetic field is coming out of the paper. θ is a fixed angle made by PQ travelling smoothly over two conducting parallel wires separated by a distance d.
F is the force acting on PQ's free charge particle. The motional emf is calculated by multiplying E along the PQ by the effective length of the PQ. As a result, the induced current will be vBd/R,...
Consider a closed loop C in a magnetic field such that the flux passing through the loop is defined by choosing a surface whose edge coincides with the loop and using the formula φ= B1dA1 + B2dA2 + …. Now if we chose two different surfaces S1 and S2 having C as their edge, would we get the same answer for flux. Justify your answer.
The magnetic flux lines that pass through are identical to those that flow through the surface. The magnetic field lines in an area A with magnetic flux B are represented by = B1dA1 + B2dA2. As a...
A magnetic field in a certain region is given by B = Bo cos ωt k and a coil of radius a with resistance R is placed in the x-y plane with its centre at the origin in the magnetic field. Find the magnitude and the direction of the current at (a, 0, 0) at t =π ω /2, t =π /2ω and t =3π/ω
The magnetic field is directed along the z-axis. B.A = BA cos = B.A cos = B.A cos = B.A cos = B.A cos Using the electromagnetic induction law of Faraday, R sin t = Boa2/R sin t = I = Boa2/R sin t =...
Consider a metallic pipe with an inner radius of 1 cm. If a cylindrical bar magnet of radius 0.8cm is dropped through the pipe, it takes more time to come down than it takes for a similar unmagnetised cylindrical iron bar dropped through the metallic pipe. Explain.
The magnetic flux across the pipe changes when a cylindrical bar magnet with a radius of 0.8 cm is dropped through it, causing eddy currents to form. The existence of eddy current causes the magnet...
Consider a metal ring kept (supported by a cardboard) on top of a fixed solenoid carrying a current I. The centre of the ring coincides with the axis of the solenoid. If the current in the solenoid is switched off, what will happen to the ring?
We already know that current was flowing through the solenoid, causing it to act like a magnet with the S pole on the upper side. As a result, the ring has no induced current. When the current is...
Consider a metal ring kept on top of a fixed solenoid such that the centre of the ring coincides with the axis of the solenoid. If the current is suddenly switched on, the metal ring jumps up. Explain.
The metal ring leaps up when the current is quickly turned on because the magnetic flux across the ring is enhanced.
A solenoid is connected to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, will the current increase or decrease? Explain.
The magnetic flux rises when an iron core is introduced into the solenoid. According to Lenz's law, as the flux increases, the current flow through the coil decreases.
A wire in the form of a tightly wound solenoid is connected to a DC source, and carries a current. If the coil is stretched so that there are gaps between successive elements of the spiral coil, will the current increase or decrease? Explain.
When the spiral coil is extended and there are gaps between consecutive components, the current rises. Reactance must drop in order for current to rise.
Consider a magnet surrounded by a wire with an on/off switch S. If the switch is thrown from the off position (open circuit) to the on position (closed circuit), will a current flow in the circuit? Explain
There will be no current induced since there is no change in the magnet or the circuit area. In addition, there has been no change in the angle
A circular coil expands radially in a region of the magnetic field and no electromotive force is produced in the coil. This can be because (a) the magnetic field is constant. (b) the magnetic field is in the same plane as the circular coil and it may or may not vary. (c) the magnetic field has a perpendicular (to the plane of the coil) component whose magnitude is decreasing suitably. (d) there is a constant magnetic field in the perpendicular (to the plane of the coil) direction.
(b) the magnetic field is in the same plane as the circular coil and it may or may not vary. (c) the magnetic field has a perpendicular (to the plane of the coil) component whose magnitude is...
The mutual inductance M12 of coil 1 with respect to coil 2 (a) increases when they are brought nearer. (b) depends on the current passing through the coils. (c) increases when one of them is rotated about an axis. (d) is the same as M21 of coil 2 with respect to coil 1.
(a) increases when they are brought nearer. (d) is the same as M21 of coil 2 with respect to coil 1.
An e .m.f is produced in a coil, which is not connected to anexternal voltage source. This can be due to (a) the coil is in a time-varying magnetic field. (b) the coil moving in a time-varying magnetic field. (c) the coil moving in a constant magnetic field. (d) the coil is stationary in an external spatially varying magnetic field, which does not change with time.
(a) the coil is in a time-varying magnetic field. (b) the coil moving in a time-varying magnetic field. (c) the coil moving in a constant magnetic field.
A metal plate is getting heated. It can be because (a) a direct current is passing through the plate. (b) it is placed in a time-varying magnetic field. (c) it is placed in a space varying magnetic field, but does not vary with time. (d) a current (either direct or alternating) is passing through the plate.
(a) The plate is receiving a direct current. (b) it is exposed to a magnetic field that changes over time. (c) it is put in a magnetic field that varies in space but not in time.
The self-inductance L of a solenoid of length l and area of cross-section A, with a fixed number of turns N increases as (a) l and A increase. (b) l decreases and A increases. (c) l increases and A decreases. (d) both l and A decrease.
(b) l decreases and A increases.
Same as problem 4 except the coil A is made to rotate about a vertical axis. No current flows in B if A is at rest. The current in coil A, when the current in B (at t = 0) is counterclockwise and the coil A is as shown at this instant, t = 0, is (a) constant current clockwise. (b) varying current clockwise. (c) varying current counterclockwise. (d) constant current counterclockwise.
(a) clockwise steady current
There are two coils A and B. A current starts flowing in B as shown, when A is moved towards B and stops when A stops moving. The current in A is counterclockwise. B is kept stationary when A moves. We can infer that (a) there is a constant current in the clockwise direction in A. (b) there is a varying current in A. (c) there is no current in A. (d) there is a constant current in the counterclockwise direction in A.
(d) In A, there is a counterclockwise current that is constant.
A cylindrical bar magnet is rotated about its axis. A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then (a) a direct current flows in the ammeter A. (b) no current flows through the ammeter A. (c) an alternating sinusoidal current flows through the ammeter A with a time period T=2π/ω. (d) a time-varying non-sinusoidal current flows through the ammeter A.
(b) There is no current flowing through ammeter A.
A loop, made of straight edges has six corners at A(0,0,0), B(L,O,0) C(L,L,0), D(0,L,0) E(0,L,L) and F(0,0,L). A magnetic field B = Bo (i + k)T is present in the region. The flux passing through the loop ABCDEFA (in that order) is (a) Bo L2 Wb. (b) 2 Bo L2 Wb. (c) 2 Bo L2 Wb. (d) 4 Bo L2 Wb.
(b) 2 Bo L2 Wb. is the correct answer
A square of side L meters lies in the x-y plane in a region, where the magnetic field is given by B = Bo (2i + 3j + 4k) T where Bo is constant. The magnitude of flux passing through the square is (a) 2 Bo L2 Wb. (b) 3 Bo L2 Wb. (c) 4 Bo L2 Wb. (d) √29 B Lo2 Wb
(c) 4 Bo L2 Wb. is the correct answer
A thin circular loop of radius R rotates about its vertical diameter with an angular frequency ω. Show that a small bead on the wire loop remains at its lowermost point for ω ≤ √g / R . What is the angle made by the radius vector joining the centre to the bead with the vertically downward direction for ω = √2g/ R ? Neglect friction.
Let θ be the angle made by the radius vector joining the bead and the centre of the wire with the downward direction. Let, N be the normal reaction mg = N cosθ —–(1) mrω2 = Nsinθ —– (2) (or) m...
The rear side of a truck is open and a box of 40 kg mass is placed 5 m away from the open end as shown in Fig. The coefficient of friction between the box and the surface below it is 0.15. On a straight road, the truck starts from rest and accelerates with 2 ms-2. At what distance from the starting point does the box fall off the truck? (Ignore the size of the box).
F = ma = 40 x 2 = 80 N is the force experienced by the box. Ff = mg = 0.15 x 40 x 10 = 60 N Frictional force F – Ff = 80 – 60 = 20 N Net force = F – Ff = 80 – 60 = 20 N In the box, a =20/40(Net...
A block of mass 15 kg is placed on a long trolley. The coefficient of static friction between the block and the trolley is 0.18. The trolley accelerates from rest with 0.5 ms-2 for 20 s and then moves with uniform velocity. Discuss the motion of the block as viewed by (a) a stationary observer on the ground, (b) an observer moving with the trolley.
The block's mass is 15 kg. Static friction coefficient between the block and the trolley, p= 0.18 The trolley accelerates at a rate of 0.5 m/s2. (a) The force experienced by the block, F = ma = 15 x...
Ten one rupee coins are put on top of one another on a table. Ten one rupee coins are put on top of one Each coin has a mass of m kg. Give the magnitude and direction of the reaction of the sixth coin on the seventh coin.
(c) The sixth coin is pressed against the four coins above it, which are pulling it downward. The 6th coin has a total downward force of 4mg. The 6th coin will exert a reaction force upwards,...
. A stone of mass m tied to the end of a string is revolving in a vertical circle of radius R. The net force at the lowest and highest points of the circle directed vertically downwards are: (choose the correct alternative).
T1 and v1 denote the tension and speed at the lowest point. T2 and v2 denote corresponding values at the highest point. (mg – T1) is the net force at the lowest position, and (mg + T2) is the net...
Figure shows a man standing stationary with respect to a horizontal conveyor belt that is accelerating with 1 ms-2. What is the net force on the man? If the coefficient of static friction, between the man’s shoes and the belt is 0.2, up to what acceleration of the belt can the man continue to be stationary relative to the belt? (Mass of the man = 65 kg.)
Here, the conveyor belt's acceleration is a = 1 ms-2. s=0.2 is the static friction coefficient. m = 65 kg m = 65 kg m = 65 kg m = 65 kg m = 65 kg Ma = 65 x 1 = 65N is the Net Force. The friction...
Explain why a horse cannot pull a cart and run in empty space,
When the horse pulls the cart, it exerts a certain amount of force on the ground. The ground will exert an equal and opposite reaction force on the horse's feet if the third rule of motion is...
A stone of mass 0.25 kg tied to the end of a string is whirled round in a circle of radius 1.5 m with a speed of 40 rev./min in a horizontal plane. What is the tension in the string? What is the maximum speed with which the stone can be whirled around if the string can withstand a maximum tension of 200 N?
The stone weighs 0.25 kilogramme. r = 1.5 m Radius n= 40/60 = (23) rev/sec is the number of revolutions per second. = 2n = 2 x 3.14 x (23) is the angular velocity. The centripetal force is provided...
A batsman deflects a ball by an angle of 45° without changing its initial speed which is equal to 54 km/h. What is the impulse imparted to the ball? (Mass of the ball is 0.15 kg.)
The ball's speed is 54 km/h. The ball is deflected backwards to a total angle of 450 degrees. The initial momentum of the ball is mucosӨ = (0.15 x 54 x 1000 x cos 22. 5)/3600 = 0.15 x 15 x 0.9239...
A shell of mass 0.020 kg is fired by a gun of mass 100 kg. If the muzzle speed of the shell is 80 ms-1.What is the recoil speed of the gun?
m = 0.020 kg is the mass of the shell. M is the gun's mass, which is 100 kilogrames. The shell's speed is 80 m/s. The shell's and gun's initial velocity is both zero. As a result, the system's...
Two billiard balls, each of mass 0.05 kg, moving in opposite directions with speed 6 ms-1 collide and rebound with the same speed. What is the impulse imparted to each ball due to the other?
Each ball has a mass of 0.05 kg. Each ball's initial velocity is 6 m/s. Before the impact, each ball's initial momentum 0.3 kg m/s = 0.05 x 6 The direction of motion of the balls changes after the...
A nucleus is at rest in the laboratory frame of reference. Show that if it disintegrates into two smaller nuclei, the products must move in opposite directions.
Let m1, m2 be the masses of the two daughter nuclei, and v1, v2 be the daughter nuclei's respective velocities. Let m be the parent nucleus's mass. After disintegration, total linear momentum = m1v1...
Two masses 8 kg and 12 kg are connected at the two ends of a light inextensible string that goes over a frictionless pulley. Find the acceleration of the masses and the tension in the string when the masses are released.
According to the question, m1 = 8 kg m2 = 12 kg Tension = T The heavier mass m2 will move downwards and the smaller mass m1 will move upwards. On Applying Newton’s second law, For mass m1: T – m1g =...
Two bodies of masses 10 kg and 20 kg respectively kept on a smooth, horizontal surface are tied to the ends of a tight string. A horizontal force F = 600 N is applied to (i) A, (ii) B along the direction of string. What is the tension in the string in each case?
Given, A body mass of 10 kilogrames (m1) B, m2 = 20 kg, 600 N horizontal force m = m1 + m2 = 30 kg is the total mass of the system. Using Newton's second rule of motion, we can calculate ma = f...
Figure shows the position-time graph of a particle of mass 4 kg. What is the (a) force on the particle for t 4 s, 0 < t < 4 s? (b) impulse at t = 0 and t = 4 s? (Consider one-dimensional motion only).
When t<0, the particle's distance travelled is zero. As a result, the particle's force is zero. When 0< t< 4s occurs, the particle is travelling at a constant speed. As a result, there will...
A bob of mass 0.1 kg hung from the ceiling of a room by a string 2 m long is set into oscillation. The speed of the bob at its mean position is 1 ms-1. What is the trajectory of the bob if the string is cut when the bob is at one of its extreme positions?
(a) The velocity of the bob is zero when it is at one of its extreme positions. If the string is severed, the bob will fall vertically downward due to its weight F = mg.
A truck starts from rest and accelerates uniformly at 2.0 ms-2. At t = 10 s, a stone is dropped by a person standing on the top of the truck (6 m high from the ground). What are the (a) velocity, and (b) acceleration of the stone at t = 11s? (Neglect air resistance.)
u = 0 is the initial velocity. a = 2 ms-2, a = 2 ms-2, a = 2 ms-2, a = 2 m t=10s t=10s t=10s t=10 We get v = u + at using the equation v = u + at. 20 m/s = v = 0 + 2 x 10 ...
A body of mass 0.40 kg moving initially with a constant speed of 10 ms-1 to the north is subject to a constant force of 8.0 N directed towards the south for 30 s. Take the instant the force is applied to be t = 0, the position of the body at that time to be x = 0, and predict its position at t = -5 s, 25 s, 100 s.
Given, Body mass is 0.40 kg. u = 10 m/s initial velocity f = -8 N force (retarding force) Using the formula S = ut + (12) at2, (a) At time t = – 5 s, position From t = 0 s, the force acts on the...
A rocket with a lift-off mass of 20,000 kg is blasted upwards with an initial acceleration of 5.0 ms-2. Calculate the initial thrust (force) of the blast.
Given, m = 20000 kg = 2 x 104 kg Initial acceleration = 5 ms-2 g = 9.8 m/s2 The initial thrust (force) should provide a 5 ms-2 upward acceleration and should overcome gravity. As a result of the...
The driver of a three-wheeler moving at a speed of 36 km/h sees a child standing in the middle of the road and brings his vehicle to rest in 4.0 s just in time to save the child. What is the average retarding force on the vehicle? The mass of the three-wheeler is 400 kg, and the mass of the driver is 65 kg.
Given, u=36 km/h is the initial velocity. v = 0 is the final velocity. The three-mass wheeler's is m1=400 kg. The driver's mass is m2 = 65 kg. The time it took to bring the car to a complete stop...
A body of mass 5 kg is acted upon by two perpendicular forces 8 N and 6 N. Give the magnitude and direction of the acceleration of the body.
According to the question, m = 5 kg F1 = 8N ,F2 = 6N Resultant force of the body F = \sqrt{F_{1}^{2}+F_{2}^{2}}=\sqrt{8^{2}+6^{2}}= \sqrt{64+36}=10NF=F12+F22=82+62=64+36=10N , a = F/m a = 10/ 5...
. A constant retarding force of 50 N is applied to a body of mass 20 kg moving initially with a speed of 15 m s-1. How long does the body take to stop?
Here, – 50 N force (since it is a retarding force) m = 20 kg mass 0 = v u = 15 m s-1 u = 15 m s-1 u = 15 m F = ma force a = F/m = -50/20 = – 2.5 ms-2 v = u + at is the equation to use. 0 = 15 + (-...
One end of a string of length l is connected to a particle of mass m and the other to a small peg on a smooth horizontal table. If the particle moves in a circle with speed v the net force on the particle (directed towards the centre) is : (i) T (ii) T – mv2/l (iii) T + mv2/l (iv) 0 T is the tension in the string. [Choose the correct alternative].
T is the particle's net force, and it is directed towards the centre. It gives the particle the centrifugal force it needs to travel in a circle.
Give the magnitude and direction of the net force acting on a stone of mass 0.1 kg, (a) just after it is dropped from the window of a stationary train (b) just after it is dropped from the window of a train running at a constant velocity of 36 km/h (c ) just after it is dropped from the window of a train accelerating with1 m s-2 (d) lying on the floor of a train which is accelerating with 1 m s-2, the stone being at rest relative to the train. Neglect air resistance throughout.
(a) Stone mass = 0.1 kg 10 ms^(-2)= acceleration F = mg = 0.1 x 10 = 1.0 N is the net force. The force is applied vertically and downwards. (b) The train maintains a steady...
A pebble of mass 0.05 kg is thrown vertically upwards. Give the direction and magnitude of the net force on the pebble, (a) during its upward motion (b) during its downward motion (c) at the highest point where it is momentarily at rest. Do your Solutions change if the pebble was thrown at an angle of 45° with the horizontal direction? Ignore air resistance
(a) The acceleration due to gravity acts downwards throughout the upward motion of the pebble, thus the magnitude of the force on the pebble is 0.5 N = F = mg = 0.05 kg x 10 ms-2 The force is in a...
1. Give the magnitude and direction of the net force acting on (a) a drop of rain falling down with a constant speed (b) a cork of mass 10 g floating on water (c) a kite skillfully held stationary in the sky (d) a car moving with a constant velocity of 30 km/h on a rough road (e) a high-speed electron in space far from all material objects, and free of electric and magnetic fields.
(a)The raindrop continues to fall at the same rate. As a result, the acceleration will be zero. Because F = ma, the force exerted on the drop will be zero when the acceleration is zero. (b) The cork...
A geyser is rated 1500 W, 250 V. This geyser is connected to 250 V mains. Calculate:
(i)The current drawn,
(ii)The energy consumed in 50 hours, and
(iii)The cost of energy consumed at ₹ 4.20 per kWh.
We know that Geyser power, P = 1500 W , V = 250 V (i) since, Current, I = P / V thus, I = 1500 / 250 I = 6 A (ii) Time, t = 50 h Energy, E = P × t E = 1500 × 50 E = 75000 Wh E = 75 kWh (iii) hence...
An electric kettle is rated 2.5 kW, 250 V’. Find the cost of running the kettle for two hours at ₹ 5.40 per unit
We know that, kettle power, P = 2.5 kW Potential difference V = 250 V t = 2 h since, Energy, E = P × t E = 2.5 × 2 E = 5 kWh Cost per unit of energy = ₹ 5.40 Cost for 5 kWh of energy = 5.40 × 5 = ₹...
An electric toaster draws current 8 A in a circuit with source of voltage 220 V. It is used for 2 h. Find the cost of operating the toaster if the cost of electrical energy is ₹ 4.50 per kWh
According to the question, Given that V = 220 V I = 8 A , t = 2 h E = VIt We know that E = 220 × 8 × 2 E = 3520 Wh E = 3.52 kWh Therefore, Cost of 3.52 kWh energy is ₹ 4.50 × 3.52 kWh= ₹...
Water in an electric kettle connected to a 220 V supply took 5 minutes to reach its boiling point. How long will it take if the supply had been of 200 V?
According to the question, \(P={{V}^{2}}/R\) Heat gained = (\{{V}^{2}}/R\times t\) (V12 / R) × t1 = (V22 / R) × t2 t2 = (V1 / V2)2 × t1 This implies that t2 = 6.05 min.
A battery of e.m.f. 15 V and internal resistance 2 ohm is connected to two resistors of resistances 4 ohm and 6 ohm joined in series. Find the electrical energy spent per minute in 6 ohm resistor.
According to the question, battery emf V = 15 V RB = 2 ohm (Internal resistance of battery) Resistances given in circuit are 4 ohm and 6 ohm respectively. (i) In series, Equivalent resistance, R =...
Two resistors A and B of 4 ohm and 6 ohm, respectively are connected in parallel. The combination is connected across a 6 volt battery of negligible resistance. Calculate: (i) the power supplied by the battery, (ii) the power dissipated in each resistor.
Provided, RA = 4 ohm resistance RB = 6 ohm resistance V = 6 V is the voltage. (i)Due to the parallel connection of the resistances 1 / R = 1 / 4 + 1 / 6 1 / R = 10 / 24 R = 2.4 ohm We are aware of...
A bulb is connected to a battery of p.d. 4 V and internal resistance 2.5 ohm. A steady current of 0.5 A flows through the circuit. Calculate:
(i)The total energy supplied by the battery in 10 minutes,
(ii)The resistance of the bulb, and
(iii)The energy dissipated in the bulb in 10 minutes.
We know that, V = 4 V is the voltage. 2.5 ohm is the battery resistance. I = 0.5 A (current) E = V2t / R (Energy supplied by the battery) t = 10 × 60 t = 600 sec R = V / I R = 4 / 0.5 R = 8 ohm E =...
Three heaters each rated 250 W, 100 V are connected in parallel to a 100 V supply. Calculate:
(i)The total current taken from the supply,
(ii)The resistance of each heater, and
(iii)The energy supplied in kWh to the three heaters in 5 hours.
Given, P = 250 W V = 100 V is the voltage. I =? (Current flowing through each heater) Because P = VI I = P / V I = 250 / 100 I = 2.5 A ∴ For the three heaters, current was taken. = 3 × 2.5 = 7.5 A...
An electric bulb is rated 250 W, 230 V.
(i) the energy consumed in one hour, and
(ii) the time in which the bulb will consume 1.0 kWh energy when connected to 230 V mains?
We know that, P = 250 W(Power) V = 230 V(Voltage) (i) E = P × t t = 3600 sec Given that, E = 250 × 3600 E = 9 × 105 J (ii) 1000 Wh = 250 × t Hence, time,=4 hours
Two bulbs are rated 60 W, 220 V and 60 W, 110 V, respectively. Calculate the ratio of their resistances.
Given, V1 = 220 V voltage 110 volts V2 , P1 = P2 = P = 60 W We are aware of this. V2 / P = R R1 = V12 / P R1 = (220)2 / 60 R2 = V22 / P R2 = (110)2 / 60 Now, if we divide R1 and R2 together, we...
What is the resistance, under normal working conditions, of an electric lamp rated at ‘240 v’, 60 W? If two such lamps are connected in series across a 240 V mains supply, explain why each one appears less bright.
Given, V Equals 240 V Voltage P = 60 W We are aware of this. P = V2 / R R = V2 / P R = (240)2 / 60 R = 960 ohm I = P / V I = 60 / 240 I = 0.25 A When one lamp is connected across the mains, the...
A current of 0.2 A flows through a wire whose ends are at a potential difference of 15 V. Calculate:
(i)The resistance of the wire, and
(ii)The heat energy produced in 1 minute.
Given, I = 0.2 A current V = 15 V potential difference t = 60 seconds Because V = IR, (a) Determining the wire's resistance V / I = R R = 0.2 / 15 R = 75 ohm (b) Determine the amount of heat energy...
A bulb rated 12 V, 24 W operates on a 12 volt battery for 20 minutes. Calculate:
(i) the current flowing through it, and
(ii) the energy consumed.
We know that, P = 24 W (power) V = 12 V is the voltage. I =? We are aware of this. P = VI = Power (i) It has a current running through it. I = 12 / 24 2 A = I (ii) Energy, E = P × t E = 24 × 20 × 60...
An electric press is rated ‘750 W, 230 V’. Calculate the electrical energy consumed by the press in 16 hours
According to the question, P=750W P.D=230 V We know that E = Power × time E = 750 × 16 E = 12000 Wh Hence, E = 12 kWh
An electric bulb is rated at 220 V, 100 W. (a) What is its resistance? (b) What safe current can be passed through it?
(a) Assume P = 100 W V = 220 V is the voltage. We are aware of this. P = V2 / R = Power R = (220)2 / 100 484 ohm (b) The current that may be safely carried through it is P / V = I I = 220 / 100 0.45...
An electric bulb is rated ‘100 W, 250 V’. How much current will the bulb draw if connected to a 250 V supply?
We know that, P = 100 W V Equals 250 V Voltage We are aware of this. P = VI = Power P / V = I I = 100 / 250 0.4 A = I
Calculate the current through a 60 W lamp rated for 250 V. If the line voltage falls to 200 V, how is power consumed by the lamp affected?
We know that, P = 60 W V = 250 V Let us consider, P = VI I = 60 / 250 This implies I = 0.24 A We know Resistance of lamp R = V2 / P R = (250)2 / 60 R = 1041.6 ohm If the voltage drops to 200 V, the...
A current of 2 A is passed through a coil of resistance 75 Ω for 2 minutes.
(a) How much heat energy is produced?
(b) How much charge is passed through the resistance?
According to the question, Given that (I) = 2 A R = 75 Ω t = 120 s (a)so, Heat produced, H = I2Rt or H = (2)2 (75) (120) J = 36000 J (b) We know that Q = It or Q = (2) (120) C Therefore, Q = 240 C...
An electric bulb of resistance 500 ohm draws current 0.4 A from the source. Calculate: (a) the power of bulb and (b) the potential difference at its end.
We know that, Electric bulb resistance (R) = 500 ohm (I) = 0.4 A current taken from the source (a) The bulb's power (P) is equal to VI. V = I R V = 0.4500 V (b) At the other end, the potential...
An electrical appliance has a rating 100 W, 120 V. The resistance of element of appliance when in use is:
(a) 1.2 ohm
(b) 144 ohm
(c) 120 ohm
(d) 100 ohm
When in use, the resistance of the appliance's element is 144 ohm.
Name the factors on which the heat produced in a wire depends when current is passed in it, and state how does it depend on the factors stated by you.
The quantity of heat created in a wire when current is sent through it is determined by the three elements listed below. I The current that flows through the wire (ii) The wire resistance and (iii)...
Two lamps, one rated 220 V, 50 W and the other rated 220 V, 100 W, are connected in series with mains of voltage 220 V. Explain why does the 50 W lamp consume more power.
A 220 V, 50 W light has a resistance of \({R}_{1}={{V}^{2}}/{{P}_{1}}\) \({R}_{1}={{220}^{2}}/{{100}}\) R1 is equal to 968 ohm. A light with a resistance of 220 V and a power of 100 W is...
Complete the following:
(a) 1 kWh = (1 volt × 1 ampere × ……..) / 1000
(b) 1 kWh= ________ J
(a) \(1KWh=\frac{(1volt\times 1ampere\times 1hour)}{1000}\) (b) \(1KWh=3.6\times {{10}^{6}}\)J
How do kilowatt and kilowatt-hour differ?
The kilowatt-hour is an electrical energy unit, whereas the kilowatt is an electrical power unit.
(i)State and define the household unit of electricity.
(ii)What is the voltage of the electricity that is generally supplied to a house?
(iii) What is consumed while using different electrical appliances, for which electricity bills are paid?
(i)The residential unit of electricity is the kilowatt hour (kWh). When an electrical device with a power of 1 kW is operated for one hour, the electrical energy used is A kilowatt hour is a unit of...
State the S.I. unit of electrical power.
The S.I. unit of electrical power is the watt.
Explain the meaning of the statement ‘the power of an appliance is 100 W’.
An appliance's power is 100 watts. This implies that the device consumes 100 J of electrical energy in a single second.
Name the S.I. unit of electrical energy. How is it related to Wh?
The S.I. unit of electrical energy is the joule. It has something to do with Wh. 3600 J = 1 Wh
Electrical power P is given by the expression P = (Q × V) ÷ time
(a)What do the symbols Q and V represent?
(b)Express the power P in terms of current and resistance explaining the meanings of symbols used there in.
(a) The letters Q and V stand for charge and voltage, respectively. \(P={{I}^{2}}R\) (b) Electrical Power -where I stands for current and R stands for resistance
Write an expression for the electrical power spent in flow of current through a conductor in terms of (a) resistance and potential difference, (b) current and resistance.
(a) In terms of resistance and potential difference, the electrical power expended in current flow through a conductor is expressed as Electrical Power=\(P={{v}_{2}}/R\) (b) In terms of current and...
Write an expression for the electrical energy spent in flow of current through an electrical appliance in terms of current, resistance and time.
In terms of current, resistance, and time, the electrical energy consumed in the passage of current through an electrical device is expressed as \(W={{I}^{2}}RT\)joule, electrical energy
A cell of e.m.f. 2 V and internal resistance 1.2 Ω is connected to an ammeter of resistance 0.8 Ω and two resistors of 4.5 Ω and 9 Ω as shown in fig.
Find:
(a) The reading of the ammeter,
(b) The potential difference across the terminals of the cells, and
(c) The potential difference across the 4.5 ohm resistor.
We know that, \({{R}_{eq}}\) = 1.2 + 0.8 + (R1R2) / R1 + R2 \({{R}_{eq}}\) = 2 + 40.5 / 13.5 This implies that \({{R}_{eq}}\) = 5 ohm (a) So, the current is I = \({{E}_{cell}}\) /\({{R}_{eq}}\) I =...
The diagram below in Fig., shows the arrangement of five different resistances connected to a battery of e.m.f. 1.8 V. Calculate:
a. The total resistance of the circuit
b. The reading of ammeter A.
(a)According to the question, in the diagram given Let us consider that RXY be the resistance between X and Y Therefore, 1 / RXY = 1 / 10 + 1 / 40 1 / RXY = 5 / 40 ohm This implies RXY = 8 ohm Let...
Three resistors of 6.0 ohm, 2.0 ohm and 4.0 ohm are joined to an ammeter A and a cell of emf 6.0 V as shown in figure. Calculate:
(a) the efective resistance of the circuit.
(b) the reading of ammeter
(a) According to the question, Given R1 = 6 W R’ = R2 + R3 R’ = 2 + 4 R’ = 6 W R1 and R’ are joined in parallel 1 / R = 1 / R1 + 1 / R’ 1 / R = 1 / 6 + 1 / 6 1 / R = 2 / 6 1 / R = 1 / 3 R = 3 ohm...
The circuit diagram in figure shows three resistors 2 ohm, 4 ohm and R ohm connected to a battery of e.m.f. 2 V and internal resistance 3 ohm. If main current of 0.25 A flows through the circuit, find:
(a) the p.d. across the 4 ohm resistor
(b) the p.d. across the internal resistance of the cell,
(c) the p.d. across the R ohm or 2 ohm resistor, and
(d) the value of R.
(a) According to the question, find p.d. across the resistor of 4 ohm. Given, R = 4 ohm I = 0.25 A Using ohm's law V = IR V = 0.25 × 4 V = 1 V (b) According to the question, find p.d. across the...
A battery of emf 15 V and internal resistance 3 ohm is connected to two resistors 3 ohm and 6 ohm connected in parallel. Find (a) the current through the battery (b) p.d. between the terminals of the battery (c) the current in 3 ohm resistor (d) the current in 6 ohm resistor.
(a) According to the question, When In parallel 1 / R = 1 / 3 + 1 / 6 1 / R = 1 / 2 R = 2 ohm If r = 3 W ε = 15 V ε = I (R + r) 15 = I (2 + 3) I = 3 A (b) Now find V R = 2 ohm Using ohm's law V =...
A cell supplies a current of 1.2 A through two 2 ohm resistors connected in parallel. When resistors are connected in series, it supplies a current of 0.4 A. Calculate: (i) the internal resistance and (ii) e.m.f. of the cell.
According to the question, As we know that In parallel R = 1 / 2 + 1 / 2 = 1 ohm I = 1.2 A ε = I (R + r) ε = 1.2 (1 + r) ε = 1.2 + 1.2r In series R = 2 + 2 R = 4 ohm I = 0.4 A ε = I (R + r) ε = 0.4...
A particular resistance wire has a resistance of 3 ohm per meter. Find:
(a) The total resistance of three lengths of this wire each 1.5 m long, in parallel.
(b) The potential difference of the battery which gives a current of 2 A in each of the 1.5 m length when connected in the parallel to the battery (assume that resistance of the battery is negligible).
(c) The resistance of 5 m length of a wire of the same material, but with twice the area of cross section
(a) Wire resistance per metre = 3 ohm As a result, the resistance of three 1.5 m long sections of this wire = 3 × 1.5 = 4.5 W 1 / R = 1 / 4.5 + 1 / 4.5 + 1 / 4.5 1 / R = 3 / 4.5 R = 1.5 ohm (b) I =...
Two resistors of resistance 4 Ω and 6 Ω are connected in parallel to a cell to draw 0.5 A current from the cell.
(a) Draw a labeled diagram of the arrangement
(b) Calculate current in each resistor.
(a) Circuit diagram (b) Equivalent resistance of the circuit 1 / R = 1 / 4 + 1 / 6 1 / R = (3 + 2) / 12 1 / R = 5 / 12 R = 12 / 5 R = 2.4 ohm Hence, the e.m.f. of the cell is V = IR V = 0.5 × 2.4 V...
Two resistors of 2 ohm and 3 ohm are connected (a) in series, (b) in parallel, with a battery of 6.0 V and negligible internal resistance. For each case draw a circuit diagram and calculate the current through the battery.
According to the question, (a)R1 = 2 ohm R2 = 3 ohm R = R1 + R2 R = 2 + 3 R = 5 ohm V = 6 V Now, I = V / R I = 6 / 5 I = 1.2 ohm when, R1 and R2 are joined in parallel 1 / R = 1 / R1 + 1 / R2...
In the network shown in adjacent figure, calculate the equivalent resistance between the points (a) A and B (b) A and C
According to the question, (a) R1 = 2 + 2 + 2 R1 = 6 ohm R2 = 2 ohm R1 and R2 are joined in parallel 1 / R = 1 / R1 + 1 / R2 1 / R = 1 / 6 + 1 / 2 1 / R = (1 + 3) / 6 1 / R = 4 / 6 R = 6 / 4 R = 1.5...
Calculate the equivalent resistance between the points A and B in figure
According to the question, R1 = 3 + 2 = 5 ohm R2 = 30 W R3 = 6 + 4 = 10 ohm If the resistors R1, R2 and R3 are connected in parallel 1 / R = 1 / R1 + 1 / R2 + 1 / R3 1 / R = 1 / 5 + 1 / 30 + 1 / 10...
Calculate the effective resistance between the points A and B in the network shown below in figure.
According to the question, If the R is parallel 1 / R = 1 / 12 + 1 / 6 + 1 / 4 1 / R = (1 + 2 + 3) / 12 1 / R = 6 / 12 R = 12 / 6 R = 2 ohm Now, if the resistances are in series R = 2 + 2 + 5 R = 9...
Calculate the effective resistance between the points A and B in the circuit shown in figure
In the diagram above, Between XAY = (1 + 1 + 1), there is a resistance. = 3 ohm Between XY = 2 ohm, there is a resistance of 2 ohm. Between XBY = 6 ohm, there is a resistance of 6 ohm. Allow R' to...
In the circuit shown below in figure, calculate the value of x if the equivalent resistance between the points A and B is 4 ohm
According to the question, r1 = 4 ohm r2 = 8 ohm r3 = x ohm r4 = 5 ohm r = 4 ohm r’ = r1 + r2 r’ = 4 + 8 Hence, r’ = 12 ohm r’’ = r3 + r4 r’’ = (x + 5) ohm 1 / r = 1 / r’ + 1 / r’’ 1 / 4 = 1 / 12 +...
A combination consists of three resistors in series. Four similar sets are connected in parallel. If the resistance of each resistor is 2 ohm, find the resistance of the combination.
Resistance of every set: r1 = 2 + 2 + 2 = 6 ohm r2 = 2 + 2 + 2 = 6 ohm r3 = 2 + 2 + 2 = 6 ohm r4 = 2 + 2 + 2 = 6 ohm Now, when the these resistances are put in parallel 1 / r = 1 / r1 + 1 / r2 + 1 /...
Calculate the equivalent resistance between the points A and B in figure if each resistance is 2.0 Ω
For a parallel resistances Reff = (R1R2) / (R1 + R2) Reff = (2 × 2) / (2 + 2) Reff = 4 / 4 Reff = 1 Ω Therefore, total resistance = 2 + 2 + 1 = 5 Ω
Three resistors each of 2 W are connected together so that their total resistance is 3 W. Draw a diagram to show this arrangement and check it by calculation.
In series with one resistor, a parallel combination of two resistors. R1 = 2 ohm R2 = 2 ohm R3 = 2 ohm 1 / R’ = 1 / R1 + 1 / R2 1 / R’ = 1 / 2 + 1 / 2 1 / R’ = 1 R’ = 1 ohm R = R’ + R3 R = 1 + 2 R =...
You have three resistors of values 2 Ω, 3 Ω and 5 Ω . How will you join them so that the total resistance is less than 1 Ω? Draw diagram and find the total resistance.
The three resistors should be linked in parallel to get a total resistance of less than one. Let the total resistance be R’ Then, 1 / R’ = 1 / 2 + 1 / 3 + 1 / 5 1 / R’ = (15 + 10 + 6) / 30 1 / R’ =...
Four resistors each of resistance 2 ohm are connected in parallel. What is the effective resistance?
According to the question, R1 = 2 ohm R2 = 2 ohm R3 = 2 ohm R4 = 2 ohm 1 / R = 1 / R1 + 1 / R2 + 1 / R3 + 1 / R4 1 / R = 1 / 2 + 1 / 2 + 1 / 2 + 1 / 2 1 / R = 2 Hence, R = 0.5...
Two resistors having resistance 4 ohm and 6 ohm are connected in parallel. Find their equivalent resistance.
Let R' be the equivalent resistance of the paralleled 4 ohm and 6 ohm resistors. Then, 1 / R’ = 1 / 4 + 1 / 6 = (3 + 2) / 12 = 5 / 12 ohm or R’ = 12 / 5 R’ = 2.4 ohm
A cell of e.m.f. ε and internal resistance r sends current 1.0 A when it is connected to an external resistance 1.9 ohm. But its sends current 0.5 A when it is connected to an external resistance of 3.9 ohm. Calculate the values of e and r.
In the first instance, I = 1 A, R = 1.9 ohm ε = I (R + r) = 1 (1.9 + r) = 1.9 + r [1] In the second scenario, I = 0.5 A, R = 3.9 ohm ε = I (R + r) = 0.5 (3.9 + r) = 1.95 + 0.5r [2] [1] and [2] are...
A battery of emf 15 V and internal resistance 3 ohm is connected to two resistors of resistances 3 ohm and 6 ohm in series. Find:
(a) the current through the battery
(b) the p.d. between the terminals of the battery.
According to the question, (a) ε = 15 V R = 6 + 3 R = 9 ohm r = 3 ohm I =? I = ε / (R + r) I = 15 / (9 + 3) I = 15 / 12 I = 1.25 A (b) Current I = 1.25 A [calculated in part (a)] External resistance...
The diagram in figure shows a cell of e.m.f. ε = 2 volt and internal resistance r = 1 ohm connected to an external resistance R = 4 ohm. The ammeter A measures the current in the circuit and the voltmeter V measures the terminal voltage across the cell. What will be the readings of the ammeter and voltmeter when (i) the key K is open, and (ii) the key K is closed
(i) Ammeter reading = 0 , due to lack of current Voltage V = ε – Ir V = 2 – 0 × 1 V = 2 volt (ii) The reading on the ammeter I = ε / (R + r) I = 4 + 1 / 2 I = 2/5 I=0.4 amp Measurement of voltage...
In parallel combination of resistances:
(a) P.D. is same across each resistance
(b) Total resistance is increased
(c) Current is same in each resistance
(d) All of the above are true
In a parallel combination of resistances, P.D is the same for each resistance.
In series combination of resistances:
(a) P.d. is same across each resistance
(b) Total resistance is reduced
(c) Current is same in each resistance
(d) All of the above are true
Each resistance in a sequence of resistances has the same current.
The V-I graph for a series combination and for a parallel combination of two resistors is shown in fig. Which of the two, A or B, represents the parallel combination? Give a reason for your answer.
The straight line A has a smaller change in V than the straight line B. (which means the straight line A is less steeper than B). As a result, the straight line A denotes low resistance, whereas the...
State how are the two resistors joined with a battery in each of the following cases when:
(a) same current flows in each resistor
(b) potential difference is same across each resistor.
(c) equivalent resistance is less than either of the two resistances.
(d) equivalent resistance is more than either of the two resistances.
(a) The two resistors are connected in parallel. (b) The two resistors are connected in series. (c) The two resistors are connected in series. (d) The two resistors are connected in parallel.
How would you connect two resistors in series? Draw a diagram. Calculate the total equivalent resistance.
If current I is taken from the battery, the current through each resistor will also be I. When we individually apply Ohm's law to the two resistors, we get: V1 = IR1 V2 = IR2 V = V1 + V2 IR = IR1 +...
A cell is used to send current to an external circuit. (a) How does the voltage across its terminal compare with its emf? (b) Under what condition is the emf of the cell equal to its terminal voltage?
(a) A cell's terminal voltage V is smaller than its e.m.f. when current is taken from it. ∴ Terminal voltage < e.m.f. (b) The e.m.f. is equal to the terminal voltage when no current is...
A cell of e.m.f. ε and internal resistance r is used to send current to an external resistance R. Write expressions for (a) the total resistance of circuit, (b) the current drawn from the cell, (c) the p.d. across the cell, and (d) voltage drop inside the cell.
(a) total resistance = R + r (b) The amount of current drained from the cell ε = V + v = IR + Ir = I (R + r) I = ε / (R + r) (c) p.d. across the cell: [ε / (R + r)] × R (d) voltage drop inside the...
Name two factors on which the internal resistance of a cell depends and state how does it depend on the factors stated by you.
The following are the variables that influence a cell's internal resistance: I The electrode surface area - the greater the electrode surface area, the lower the internal resistance. (ii) The...
State two differences between the e.m.f. and terminal voltage of a cell.
E.M.F Cell 1.It is a property of the cell, meaning it is independent of the amount of current pulled from cell 2. When the cell is not in use, it is equal to the terminal voltage, but when the cell...
Explain the meaning of the terms e.m.f., terminal voltage and internal resistance of cell.
e.m.f. : The electromotive force, or e.m.f., is the potential difference between the terminals of a cell while it is in open circuit. The potential difference between the electrodes of the cell is...
The filament of a bulb takes a current 100 mA when potential difference across it is 0.2 V. When the potential difference across it becomes 1.0 V, the current becomes 400 mA. Calculate the resistance of filament in each case and account for the difference.
Using Ohm’s law V = IR R = V / I R1 = V1 / I1 R1 = 0.2 / 0.1 R1 = 2 ohm Simultaneously R2 = V2 / I2 R2 = 1 / 0.4 R2 = 2.5 ohm The wire's resistance increases as the temperature rises. As a result,...
What length of copper wire of specific resistance ohm m and radius 1 mm is required so that its resistance is 1 ohm.
According to the question, R = 1 ohm Specific resistance = 1.7× 10-8 ohm m r = 10-3 m l =? R = ρ 1 / A l = RA / ρ l = Rπr2 / ρ l = (1 × π × 10-6) / (1.7 × 10-8) l = (1 × 3.14 × 10-6) / (1.7 × 10-8)...
A wire of resistance 3 Ohm and length 10 cm is stretched to length 30 cm. Assuming that it has a uniform cross-section, what will be its new resistance?
According to the question, R = 3 Ohm l = 10 cm we get the new length as l’ = 30 cm = 3 × l R = ρ (l / A) As a result, new resistance In the same sequence, stretching length will grow and cross...
A given wire of resistance 1 Ohm is stretched to double its length. What will be its new resistance?
Let ‘I' be the length of the resistor and ‘a' be the cross-sectional area of the resistor with resistance R = 1 Ohm. When a wire is stretched to double its original length, As a result, length l' =...
Two wires of the same material and same length have radii 1 mm and 2 mm respectively. Compare (i) their resistances (ii) their specific resistance.
(i) When the radius of wire is r1 R1 = ρ (l / A1) R1 = ρ (l / πr12) (ii) When the radius of wire is r2 R2 = ρ (l / A2) R2 = ρ (l / πr22) ∴ R1: R2 will be ρ (l / πr12) : ρ (l / πr22) = r22: r12 (ii)...
In an experiment of verification of Ohm’s law, following observations are obtained.
Draw a characteristic V-I graph and use this graph to find:
(a) potential difference V when the current I is 0.5 A.
(b) current I when the potential difference V is 0.75 V.
(c) resistance in circuit
(a) When the current is 0.5 A, the potential difference is 1.25 V. (b) When the potential difference is 0.75 V, current is 0.3 A. (c) Because the graph is linear, resistance may be calculated from...
Calculate the current flowing through a wire of resistance 5 Ohm connected to a battery of potential difference 3 V.
According to the question, V = 3 V R = 5 Ohm I =? On using Ohm’s law I = V / R I = 3 / 5 Therefore, I = 0.6 A
A car bulb connected to a 12 volt battery draws 2 A current when glowing. What is the resistance of the filament of the bulb? Will the resistance be more, same or less when the bulb is not glowing.
According to the question, V = 12 V I = 2 A R =? Using Ohm’s law R = V / I R = 12 / 2 R = 6 Ohm Therefore, if bulb is not lighting, resistance will be low
A current of 1.6 mA flows through a conductor. If charge of an electron is coulomb, find the number of electrons that will pass each second through the cross section of that conductor
According to the question, I = 1.6 × 10-3 A Q = -1.6 × 10-19 coulomb t = 1 s We know I = Q / t From here, Q = 1.6 × 10-3 × 1 Therefore, Number of electrons = 1.6 × 10-3 / 1.6 × 10-19 =...
In a conductor, electrons flow from its end A to B in 2 s. Find the current flowing through the conductor.
Given The number of electrons that pass across a conductor, The number of electrons in n =\(6.25\times {{10}^{16}}\) is the number of electrons in n = \(6.25\times {{10}^{16}}\) The time it takes to...
For which of the following substances, resistance decreases with increase in temperature?
(a) Copper
(b) Mercury
(c) Carbon
(d) Platinum
For carbon, resistance diminishes as temperature rises.
Which of the following is an ohmic resistance?
(a) LED
(b) Junction diode
(c) Filament of a bulb
(d) Nichrome wire
Nichrome wire is an ohmic resistance.
Name the material used for making a fuse wire. Give a reason.
Because of its high resistivity and low melting point, a lead-tin alloy is utilised to make fuse wire.
(a) Name the material used for making the connection wires. Give reason for your answer. (b) Why should a connection wire be thick?
(a) Copper or aluminium are the materials utilised to make connection wires because they have a low specific resistance and hence have low resistance in their wires. (b) The connecting wires are...
How does (a) resistance, and (b) specific resistance of a wire depend on its (i) length, and (ii) radius?
(a) Resistance is proportional to the wire's length and inversely proportional to the square of the wire's radius. (b) A wire's specific resistance is not affected by the length or radius of the...
How does specific resistance of a semi-conductor change with the increase in temperature?
The particular resistance of a semi-conductor reduces as the temperature rises.
Name a substance of which the specific resistance remains almost unchanged by the increase in temperature.
Manganin is a chemical whose specific resistance remains nearly constant when the temperature rises.
(a) Name two factors on which the specific resistance of a wire depends? (b) Two wires A and B are made of copper. The wire A is long and thin while the wire B is Short and thick. Which will have more specific resistance?
(a) A wire's particular resistance is determined by two elements. I The substance's material and (ii) The substance's temperature (a) Because the specific resistance of a wire is determined by its...
State the order of specific resistance of (i) a metal, (ii) a semiconductor and (iii) an insulator.
I Metals have a low specific resistance because they enable the majority of current to flow through them. (ii) Semiconductors have a higher specific resistance than metals. (iii) Insulators have a...
Write an expression connecting the resistance of a wire and specific resistance of its material. State the meaning of symbols used.
The term used is R = ρ l / a where ρ = the conductor's material's specific resistance R = conductor resistance l = conductor length A = conductor cross-sectional area
Define the term specific resistance and state its S.I. unit.
A material's specific resistance is the resistance of a wire of that material of unit length and cross section area. The ohm metre is the SI unit of specific resistance.
Name three factors on which the resistance of a wire depends and state how it is affected by the factors stated by you?
The following are the three variables that influence wire resistance: (i)A wire's resistance is proportionate to its length, that is, R ∝ l (ii) A wire's resistance varies inversely with its cross...
How does the resistance of a wire depend on its length? Give a reason of your answer.
The length of a wire is directly proportional to its resistance. R ∝ l The resistance of a conductor is determined by the number of collisions that an electron has with fixed positive ions as it...
(a) How does the resistance of a wire depend on its radius? Explain your answer.
(b) Two copper wires are of same length, but one is thicker than the other. Which will have more resistance?
The resistance of a wire changes inversely with its cross-sectional area, i.e., R ∝ 1 / a R ∝ 1 / π2 The resistance of a wire is proportional to its length, i.e., R l, and inversely proportional to...
What is an ohmic resistor? Give one example of an ohmic resistor. Draw a graph to show its current – voltage relationship. How is the resistance of the resistor determined from this graph?
Ohmic resistors, often known as linear resistances, are conductors that follow Ohm's law. Silver, aluminium, copper, iron, and other metallic conductors are examples.
(a) Draw a V-I graph for a conductor obeying Ohm’s law.
(b) What does the slope of V-I graph for a conductor represent?
(a) The V-I graph for a conductor obeying Ohm's law is shown below. (b) The slope of a conductor's V-I graph reflects resistance.
(a) Name and state the law which relates the potential difference and current in a conductor.
(b) What is the necessary condition for a conductor to obey the law named above in part (a)?
(a)Ohm's law is the name of the law. The current flowing through a conductor is exactly proportional to the potential difference at its ends, assuming that the conductor's physical parameters and...
State Ohm’s law and draw a neat labelled circuit diagram containing a battery, a key, a voltmeter, an ammeter, a rheostat and an unknown resistance to verify it.
The current flowing through a conductor is exactly proportional to the potential difference applied across its ends, according to Ohm's law, assuming that the physical parameters and temperature of...
Explain the statement ‘the potential difference between two points is 1 volt’.
The potential difference between two points is said to be 1 volt when 1 joule of work is done in bringing 1 coulomb charge from infinity to that point