Question

In the circuit, the battery is ideal. A voltmeter of resistance $600\Omega$is connected in tum across $R_1$ and $R_2$. giving readings $V_1$ and $V_2$ respectively:

• A. $V_1=80V$
• B. $V_1=60V$
• C. $V_2=30V$
• D. $V_2=40V$

Answer 1

Answer: (B), (C)

$V_2=30V$
$V_1=60V$

When voltmeter is connected across $\left[R_1\right]$ ,the equivalent resistance of voltmeter's resistance and $\left[R_1\right]$ will be 300 ohm and potential drop will be same across $\left[R_1\right]$ and $\left[R_2\right]$ i.e. 60 volts.
When voltmeter is connected across $\left[R_2\right]$ ,the equivalent resistance of voltmeter's resistance and $\left[R_2\right]$ will be 200 ohm and potential drop across $\left[R_1\right]$ and $\left[R_2\right]$ will be in the ratio $\left[3/1\right]$ ,which give $[V_2=30]$ volts.