CBSE Class 10 Science 2020 · Paper 31/3/3 · Question 30(b)

Electricity 5 marks Medium

(a)What is meant by the statement, “The resistance of a conductor is one ohm” ?
(b)Define electric power. Write an expression relating electric power, potential difference and resistance.
(c)How many $132 Ω$ resistors in parallel are required to carry 5 A on a 220 V line ?

Answer

One ohm is 1 V per 1 A; power is $P = \frac{V ^{2}}{R}$ ; three $132 Ω$ resistors in parallel carry 5 A on a 220 V line.

(a) The resistance of a conductor is one ohm when a potential difference of 1 volt across its two ends makes a current of 1 ampere flow through it:

1 Ω = \frac{1 V}{1 A}

. (b) Electric power is the rate at which electrical energy is consumed or dissipated in an electric circuit. It is related to potential difference and resistance by

P = \frac{V ^{2}}{R}

. (c) The combination must have resistance

R_{p} = \frac{V}{I} = \frac{220}{5} = 44 Ω

. For

n

resistors of

132 Ω

in parallel,

R_{p} = \frac{132}{n}

, so

\frac{132}{n} = 44

and

n = 3

. Three resistors are required.

🔒 Step-by-step solution

From the board paper

CBSE Class 10 Science 2020 · Paper 31/3/3, Question 30(b) — all 30 questions with answers →

CBSE Class 10 Science 2020 · Paper 31/3/3 · Question 30(b)

Answer

From the board paper

More questions from Electricity