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. 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

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2. The SI unit of resistivity is

volt

ohm

ampere

ohm-metre

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3. 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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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 S.I. unit of electric current is:

ohm

ampere

coulomb

volt

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6. 1 kWh is the unit of ..............

electric charge

power

electric energy

electric current

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7. 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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8. The S.I. unit of electric charge is:

ohm

ampere

coulomb

volt

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

halved

unchanged

doubled

quadrupled

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11. 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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12. How is ammeter connected in an electric circuit?

Series combination

Parallel combination

both of the above

none of the above

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13. Three conducting wires of $1 \Omega, 2 \Omega \& 3 \Omega$ are connected in series in an electrical circuit. What will be the equivalent resistance?

Less than $1 \mathrm{Ohm}$

Less than $3 \mathrm{Ohm}$

More than $1 \mathrm{Ohm}$

More than $3 \mathrm{Ohm}$

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14. 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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15. Resistance of a conductor ...............

independent of length

decreases with length

increases with length

none of the above

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.