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. Resistivity depends on which of the following?

Length of the conductor

Cross section area of the conductor

Material of the conductor

None of these

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2. 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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3. Three resistances of 10 $\mathit{\Omega}$, 5 $\mathit{\Omega}$ and 2 $\mathit{\Omega}$ respectively are connected in parallel. Net resistance will be.................

more than 10$\mathit{\Omega}$

between 10$\mathit{\Omega}$ and 5$\mathit{\Omega}$

between 5$\mathit{\Omega}$ and 2$\mathit{\Omega}$

less than 2$\mathit{\Omega}$

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4. In an electric circuit voltmeter is always connected in......

series

parallel

both of the above

none of the above

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5. 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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6. 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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7. The S.I. unit of Potential Difference is:

ohm

ampere

coulomb

volt

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

ohm

ampere

coulomb

volt

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10. 1 kWh is the unit of ..............

electric charge

power

electric energy

electric current

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11. How is ammeter connected in an electric circuit?

Series combination

Parallel combination

both of the above

none of the above

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12. 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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13. Resistance of a conductor ...............

independent of length

decreases with length

increases with length

none of the above

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14. 2 ampere current flows in a conductor connected with a $5 \mathrm{~V}$ battery. Find the resistance of the conductor

$3 \Omega$

$2.5 \Omega$

$10 \Omega$

$2 \Omega$

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

$I^2R$

$I^2/R$

$VI$

$V^2/R$

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.