CBSE Class 10 Science 2019 · Paper 31/1/1/C · Question 13

Electricity 3 marks Medium

In the circuit given below, the resistors

R_{1}

R_{2}

and

R_{3}

have the values

10 Ω

20 Ω

and

30 Ω

respectively, which have been connected to a battery of

12

V. Calculate

Answer

The currents are $1.2$ A, $0.6$ A and $0.4$ A, the total resistance is $\frac{60}{11} Ω \approx 5.45 Ω$ , and the total current is $2.2$ A.

(a) Each resistor has the full

12

V across it:

I_{1} = \frac{12}{10} = 1.2

I_{2} = \frac{12}{20} = 0.6

I_{3} = \frac{12}{30} = 0.4

A. (b)

\frac{1}{R} = \frac{1}{10} + \frac{1}{20} + \frac{1}{30} = \frac{11}{60}

, so

R = \frac{60}{11} Ω \approx 5.45 Ω

. (c)

I = \frac{V}{R} = \frac{12 \times 11}{60} = 2.2

A, which equals

1.2 + 0.6 + 0.4 = 2.2

🔒 Step-by-step solution