Question

In the given circuit, calculate
i) net resistance of the circuit
ii) Voltmeter reading when
a) both the keys are open b) both the keys are closed
iii) current through 3 Ω resistor.

Answer 1

(i) step1: 3ohm and 2ohm are in series,

so, 3ohm + 2ohm=5ohm.

step 2: 5ohm at top and 5ohm just calculated are in parallel ,

then, 1/Rp=1/R1+1/R2

1/Rp=1/5 + 1/5

1/Rp=2/5

Rp=5/2

Rp=2.5ohm

(ii)  a . When key K1 will be closed, no current will pass through 5 ohm resistor , hence V = 5 I = 0. Hence, voltage difference will be 0.

b. When key K2 is closed, no current will pass through 2 and 3 ohm resistors, hence, all current will pass through 5 ohm.Hence, V across 5 ohm = 6 V = V across battery = reading of voltmeter.

(iii) V=IR

I=V/R

I=6/3

I=2 A