In the circuit shown, when switch S1 is closed and S2 is open, the ideal voltmeter shows a reading of 18 V. When switch S2 is closed and S1 is open, the reading of voltmeter is 24 V. When S1 and S2 both are closed, the voltmeter reading will be

Question

In the circuit shown, when switch S1 is closed and S2 is open, the ideal voltmeter shows a reading of 18 V. When switch S2 is closed and S1 is open, the reading of voltmeter is 24 V. When S1 and S2 both are closed, the voltmeter reading will be (A) 14.4 V (B) 20.6 V (C) 24.2 V (D) 10.8 V

Tardigrade Admin · Accepted Answer

Terminal potential difference across the terminals of cell

E

V = E - i r = E - (\frac{E}{r + R}) r = \frac{ER}{R + r}

According to question,

18 = \frac{6 E}{6 + r} ........ (i)

and

24 = \frac{12 E}{12 + r} ......... (ii)

Solving (i) and (ii), we get

r = 6 Ω, E = 36 V

When both

S_{1}

and

S_{2}

are closed, the effective external resistance in the circuit will be,

R = \frac{6 \times 12}{18} = 4 Ω

So,

V = \frac{ER}{r + R} = \frac{36 \times 4}{6 + 4} = \frac{144}{10}

V = 14.4

volt

Q. In the circuit shown, when switch S1​ is closed and S2​ is open, the ideal voltmeter shows a reading of 18V. When switch S2​ is closed and S1​ is open, the reading of voltmeter is 24V. When S1​ and S2​ both are closed, the voltmeter reading will be

14.4 V

20.6 V

24.2 V

10.8 V

Q. In the circuit shown, when switch $S_{1}$ is closed and $S_{2}$ is open, the ideal voltmeter shows a reading of $18 V$ . When switch $S_{2}$ is closed and $S_{1}$ is open, the reading of voltmeter is $24 V$ . When $S_{1}$ and $S_{2}$ both are closed, the voltmeter reading will be