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. The SI unit of resistivity is

volt

ohm

ampere

ohm-metre

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3. The frequency of alternating current in India is

45 Hertz

50 Hertz

55 Hertz

60 Hertz

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

ohm

ampere

coulomb

volt

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5. 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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6. 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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7. 1 kWh is the unit of ..............

electric charge

power

electric energy

electric current

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

Heater

Eclectic iron

Toaster

Refrigerator

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

potential difference

electric current

power

electric charge

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11. In a circuit containing two unequal resistances connected in parallel .....

the current is same in both resistors.

the current is larger in larger resistance

the voltage drop is same across both resistors

the voltage drop is larger across larger resistance

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12. 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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13. SI unit of resistance is.......

ohm

coulomb

metre

centimetre

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14. The S.I. unit of Potential Difference is:

ohm

ampere

coulomb

volt

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15. If the cross-sectional area of an aluminium wire is doubled and length remaining same, its resistivity will ......

remain same

doubled

halved

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.