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. Which of the following term does not represent electrical power in the circuit?

$I^2R$

$I^2/R$

$VI$

$V^2/R$

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2. 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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3. 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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4. The frequency of alternating current in India is

45 Hertz

50 Hertz

55 Hertz

60 Hertz

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5. The charge on an electron is........

$1.6\times {10}^{19}C$

$3.6\times {10}^{-6}C$

$3.6\times {10}^6C$

$1.6\times {10}^{-19}C$

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6. The S.I. unit of electric current is:

ohm

ampere

coulomb

volt

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7. Resistance of a conductor ...............

independent of length

decreases with length

increases with length

none of the above

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8. 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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9. Which of the device does not depend on thermal effect of current

Heater

Eclectic iron

Toaster

Refrigerator

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10. 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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11. 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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12. SI unit of resistance is.......

ohm

coulomb

metre

centimetre

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

potential difference

electric current

power

electric charge

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14. Volt is a unit of

current

potential difference

charge

work

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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.