Class 10 Science English Medium

Chapter 12: Electricity

Topics: Electric current, unit of current, potential and potential difference, prevailing symbols of useful equipments in electrical circuits, ohm’s law, resistance, dependence of resistance on length and cross-sectional area, resistivity, combination of resistances.

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1. If the length of a conductor is reduced to half (without cutting), its resistivity becomes:

half

doubled

remains same

quadrupled (four times)

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2. 1 Kilowatt hour is equal to

$3.6\times {10}^4\ J$

$3.6\times {10}^6\ J$

$3.6\times {10}^2\ J$

3.6 J

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3. Resistances of different values are connected in parallel and connected with an electrical source. In each of the resistor -

current and potential difference will be differenct

current and potential difference will be same

current will be different but potential difference will be same

d) current will be same but potential difference will be different

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4. The resistance of an electric conductor of depends on -

length of the conductor

area of cross-section of conductor

nature of material of conductor

all of the above

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5. The length of a conductor is halved. Its conductance will be ..............

halved

unchanged

doubled

quadrupled

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6. Which of the following instrument is used to measure the potential difference?

Ammeter

Voltmeter

both of the above

none of the above

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7. Work done to move 1 coulomb charge from one point to another point on a charged conductor having potential 10 volts is

1 Joule

10 Joules

Zero

100 Joules

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8. Resistance of a conductor ...............

independent of length

decreases with length

increases with length

none of the above

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9. When the temperature of a metallic conductor is increased, its resistance always...

decrease

first increase then decrease

increases

none of the above

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10. The SI unit of resistivity is

volt

ohm

ampere

ohm-metre

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11. 2 coulomb charge passes through an electrical circuit in 0.5 second. Find the value of electric current in ampere.

1 ampere

4 ampere

1.5 ampere

10 ampere

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12. The rate of doing work is called ..............

potential difference

electric current

power

electric charge

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13. Resistivity of a conductor ............

increases with the increase of its area

increases with the increase of its length

decreases with the decrease of its length

is independent of the change in its area and length.

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14. Which of the following relation is not correct for electric power (P), where symbols have their usual meanings?

P = VI

$P=V\frac{Q}{t}$

$P=I^2R$

$P=I^2Rt$

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15. An electric bulb is rated 220 V and 100W. When it is operated on 110 V, the power consumed will be:

100 W

75 W

50 W

25 W

Important Points : Electricity

Clas 10 Science MCQs of this chapter based on the following topic take a brief revision of the cahpter Electirc Current.

Electric Current:

Rate of flow of charge is called current. Its direction is always taken from positive to negative and it is measured in amperes.

Electric Resistance:

Restriction in the flow of charge is called resistance. It depends upon lenght, cross section area, temperature and the material.

Ohm's Law:

When physical states of aconductor are constant then the potential difference produced across the conductor is proportional to the current flowing through it. It is called Ohm's law.

V = IR

Where R is a constant and is known as resistance of conductor.

Measurement of Electric Current and Potential Difference:

Ammeter measures current in the circuit and is used in series in the circuit.
Voltmeter measures the potential difference across the conductor and is placed parallel to it in a circuit.

Specific Resistance:

Resistance of a conducting wire of 1 meter length and 1 square meter cross sectional area is called specific resistance of the material of the wire. Its unit is ohm $\Omega m$ i.e. ohm-metre. It does not depend on length or cross-sectional area of the wire but depends on the material of the wire.

Equivalent resistance in series combination

$$ \mathrm{R}=\mathrm{R}_{1}+\mathrm{R}_{2}+\mathrm{R}_{3} \ldots \ldots $$

Equivalent resistance in parallel combination

$$ \frac{1}{\mathrm{R}}=\frac{1}{\mathrm{R}_{1}}+\frac{1}{\mathrm{R}_{2}}+\frac{1}{\mathrm{R}_{3}}+\ldots . . $$

A pure resistor is connected to an electric source. The energy given to the pure resistor by electric source $(\mathrm{W}=\mathrm{VIt})$ fully transforms into heat energy.