Question

Consider the diagram shown below.
A voltmeter of resistance $150\Omega$ is connected across $A$ and $B$. The potential drop across $B$ and $C$ measured by voltmeter is

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

Answer 1

The correct option is C 31 V

When a voltmeter of resistance $150\Omega$ is connected across A and B, the resistance across A and B will be

$R_{ab}=\frac{150\times 100}{150+100}=60\Omega$

Now the equivalent resistance of the circuit will be $R_{ac}=R_{ab}+R_{bc}=60+100=160\Omega$

The current in the circuit will be $I=50/160=0.31A$

Thus, Potential drop across B and C will be $V_{bc}=I{R}_{bc}=\left(0.31\right)\left(100\right)=31V$