Electricity

Q36. The electrical resistivities of five substances A, B, C, S, and E are given below: A = 5.20×10-8 Ωm B = 110×10-8 Ωm C = 2.60×10-8 Ωm D = 10.0×10-8 Ωm E = 1.70×10-8 Ωmc) Which substance would you advice to be used for making heating elements of electric irons? Why? d) Which two substances should be used for making electric wires? Why?

c) B can be used in the making of the heating elements of an electric iron because the resistivity of B is the highest . d) C and E are the two substances that should be used for making electric...

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Q36. The electrical resistivities of five substances A, B, C, S, and E are given below: A = 5.20×10-8 Ωm B = 110×10-8 Ωm C = 2.60×10-8 Ωm D = 10.0×10-8 Ωm E = 1.70×10-8 Ωm a) Which substance is the best conductor of electricity? Why? b) Which one is a better conductor: A or C? Why?

Answer: a) E is the best conductor of electricity because it has the least resistivity . b) C is a better conductor between A and C because the resistivity of C is lesser than that of A .

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a) What is meant by “electric power”? Write the formula for electric power in terms of potential difference and current. b) The diagram below shows a circuit containing a lamp L, a voltmeter, and an ammeter. The voltmeter reading is 3V and the ammeter reading is 0.5A. What is the resistance and power of the lamp?

Answer: a) The rate at which electrical energy is consumed is referred to as electric power. It is given as: P = VI = watt b) Given in the question, V =...

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The diagram below depicts an electric circuit in which current passes via two resistors from a 6V battery. a)The two resistors share the current that flows from the battery. Which resistor will receive the majority of the current? b) Determine the two resistors’ effective resistance.

answer: Given, V = 6V R1 = 2Ω R2 = 3 Ω a)Because of its lower resistance, 2 ohm resistance has a larger share of current. b) Effective resistance = R 1/R = ½ + 1/3 1/R = 5/6 R = 1.2...

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Two resistance coils A and B of 24 ohm resistance each are linked to a 220V supply line on an electric heater. These coils can be utilised in a series or parallel configuration. Calculate the current drawn in the following situation: coils A and B are used in parallel

When coils A and B are utilised in parallel, the current drawn is: Total resistance is 1/R = 1/Ra + 1/Rb = 1/24 + 1/24 = 2/24 = 1/12 R = 12 ohms I = V/R = 220/12 = 18.33 amps

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Two resistance coils A and B of 24 ohm resistance each are linked to a 220V supply line on an electric heater. These coils can be utilised in a series or parallel configuration. Calculate the current drawn in the following situations: a) Only one coil A is utilized; b) coils A and B are connected in series

answer: given Ra = Rb = 24 ohm a) Current drawn when coil A is the only one used: I = V/Ra = 220/24 = 9.16 amps b) Current drawn in series when coils A and B are used: Total resistance, R = Ra + Rb...

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Two resistors with resistances of 5 and 10 should be connected to a 6V emf battery to get the minimum and maximum current flowing. a) In each situation, how will you connect the resistances? b) In both circumstances, calculate the strength of the total current in the circuit.

answer: a) When the two resistors are linked in series, the current through the resistors is kept to a minimum. The current flow is greatest when the resistors are linked in parallel. b) If the...

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The potential difference across a lamp is 12V. How many joules of electrical energy are changed into heat and light when: a) a charge of 1C passes through it? b) a charge of 5C passes through it? c) a current of 2A flows through it for 10s?

Given, Potential difference $=12 \mathrm{~V}$ a) Potential difference = (work done)/(charge moved) Work done = Potential difference$\times$ charge moved Therefore, $12 \mathrm{~J}$ of electrical...

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What is a circuit diagram? Draw the labelled diagram of an electric circuit comprising of a cell, a resistor, an ammeter, a voltmeter, and a closed switch or closed plug key. Which of the two has a large resistance: an ammeter or a voltmeter?

A circuit diagram is a graphic that uses electric symbols to show the individual components in an electric circuit and how they are connected. A voltmeter, on the other hand, will have a higher...

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Q16. a) Give two examples of substances which are good conductors of electricity. Why do you think they are good conductors of electricity? b) Calculate the resistance of a copper wire 1.0km long and 0.50mm diameter if the resistivity of copper is 1.7×10-8Ωm.

Answer: a) Two examples of substances that are good conductors of electricity are silver and copper. These two metals have free electrons that are available for conduction. b) Given in question : l...

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A 6V battery is linked in series with a 20 resistance electric bulb and a 4 resistance cable. Create a circuit schematic and perform the following calculations: c) potential difference between the electric bulb and the resistance wire d) potential difference between the electric bulb and the resistance wire

Answer: c) Difference in potential across the bulb = IR1 = 0.25 20 = 5V d) Difference in potential across the resistance wire = IR2 = 0.25 4 = 1V

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Q15. a) Write down an expression for the resistance of a metallic wire in terms of the resistivity. b) What will be the resistance of a metal wire of length 2 metres and area of cross-section 1.55×10-6m2, if the resistivity of the metal be 2.8×10-8Ωm?

Answer: a) Following is the expression for the resistance of a metallic wire in terms of the resistivity: R = ρl/A Where, R is the resistance of the wire , ρ is the resistivity of the wire , A is...

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c) An electrician has wired a house in such a way that if a lamp gets fused in one room of the house, all the lamps in other rooms of the house stop working. What is the defect in the wiring? d) Draw a circuit diagram showing two electric lamps connected in parallel together with a cell and a switch that works both lamps. Mark an A enclosed in a circle on your diagram to show where an ammeter should be placed to measure the current.

Answer: c) All of the lamps are linked together in a series combination. d)

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Ten bulbs are connected in a series circuit to a power supply line. Ten identical bulbs are connected in a: a) an identical power supply line b) which circuit would have the highest voltage across each bulb? c) in which circuit would the bulbs be brighter? d) in which circuit, if one bulb blows out, all others will stop glowing? e) which circuit would have less current in it?

Answer: The following are the right answers: c) When a parallel circuit is employed, the appliance's operation can be regulated by individual switches. d) When appliances are linked in parallel,...

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Ten bulbs are connected in a series circuit to a power supply line. Ten identical bulbs are connected in a: a) an identical power supply line b) which circuit would have the highest voltage across each bulb? c) in which circuit would the bulbs be brighter? d) in which circuit, if one bulb blows out, all others will stop glowing? e) which circuit would have less current in it?

Answer: The following are the correct answers: a) The circuit must be parallel to have an identical power supply line. b) Each bulb will have the highest voltage when the circuit is parallel.

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