Chapter 12: Electricity

Class 10 Science English Medium

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.

Online Quiz Physics for 10th

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Q. 1. 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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Q. 2. 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

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Q. 3. 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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Q. 4. SI unit of resistance is.......
	ohm
	coulomb
	metre
	centimetre

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Q. 5. Which of the device does not depend on thermal effect of current
	Heater
	Eclectic iron
	Toaster
	Refrigerator

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Q. 6. 2 coulomb charge passes through an electrical circuit in 0.5 second. Find the value of electric current in ampere.
	1 ampere
	4 ampere
	1.5 ampere
	10 ampere

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Q. 7. 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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Q. 8. How is ammeter connected in an electric circuit?
	Series combination
	Parallel combination
	both of the above
	none of the above

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Q. 9. The frequency of alternating current in India is
	45 Hertz
	50 Hertz
	55 Hertz
	60 Hertz

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Q. 10. If the length of a conductor is reduced to half (without cutting), its resistivity becomes:
	half
	doubled
	remains same
	quadrupled (four times)

Important Points : Electricity

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.