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

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