Question:
The actual value of resistance $R$, shown in the figure is $30 \Omega$. This is measured in an experiment as shown using
the standard formula $R=\frac{V}{I}$, where $V$ and $I$ are the
reading of the voltmeter and ammeter, respectively. If the measured value of $\mathrm{R}$ is $5 \%$ less, then the internal resistance of the voltmeter is:
Correct Option: , 2
Solution:
(2) using, $\frac{1}{\mathrm{R}_{\mathrm{eq}}}=\frac{1}{\mathrm{R}_{1}}+\frac{1}{\mathrm{R}_{2}}$
$0.95 \mathrm{R}=\frac{\mathrm{RRv}}{\mathrm{R}+\mathrm{Rv}}$ (measured value $5 \%$ less
then internal resistance of voltmeter)
or, $0.95 \times 30=0.05 \mathrm{Rv}$
$\therefore R v=19 \times 30=570 \Omega$