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

halved

unchanged

doubled

quadrupled

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

potential difference

electric current

power

electric charge

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7. 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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8. The electric current is due to the flow

positive charges only

negative charges only

both positive and negative charges

none of the above

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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. 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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11. The SI unit of resistivity is

volt

ohm

ampere

ohm-metre

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12. The S.I. unit of electric charge is:

ohm

ampere

coulomb

volt

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

ohm

ampere

coulomb

volt

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

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

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

$3.6\times {10}^6C$

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

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.