Question

Consider the diagram shown below.

A voltmeter of resistance $ 150 \,\Omega $ . is connected across $A$ and $B$. The potential drop across and $C$ measured by voltmeter is

• A. 29 V
• B. 27 V
• C. 31 V
• D. 30 V

Answer 1

Answer: (C)

When voltmeter is connected across $A$ and $B$, the equivalent resistance of the circuit is

$R_{e q} =100+\frac{150 \times 100}{100+150}$
$=100+\frac{15000}{250} $
$=100+60=160\, \Omega$
$\therefore $ Current, $i =\frac{50}{160}=\frac{5}{16} A$ .
Therefore, potential drop across $B$ and $C$ is
$V_{B C} =i R_{B C}$
$=\frac{5}{16} \times 100$
$=\frac{500}{16}=31.25 \,V$