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.

2287

1. Resistance of a conductor ...............

independent of length

decreases with length

increases with length

none of the above

2281

2. Which of the following relation is not correct for electric power (P), where symbols have their usual meanings?

P = VI

$P=V\frac{Q}{t}$

$P=I^2R$

$P=I^2Rt$

2737

3. The frequency of alternating current in India is

45 Hertz

50 Hertz

55 Hertz

60 Hertz

2274

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

$I^2R$

$I^2/R$

$VI$

$V^2/R$

2288

5. 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.

2278

6. SI unit of resistance is.......

ohm

coulomb

metre

centimetre

2276

7. When the temperature of a metallic conductor is increased, its resistance always...

decrease

first increase then decrease

increases

none of the above

2273

8. 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

2280

9. 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

2735

10. Volt is a unit of

current

potential difference

charge

work

2277

11. If the length of a conductor is reduced to half (without cutting), its resistivity becomes:

half

doubled

remains same

quadrupled (four times)

2740

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

Heater

Eclectic iron

Toaster

Refrigerator

2279

13. 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$\mathit{\Omega}$

2271

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

series

parallel

both of the above

none of the above

2292

15. How is ammeter connected in an electric circuit?

Series combination

Parallel combination

both of the above

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.