Question

In an experiment for calibration of voltmeter, a standard cell of emf $1.5\text{V}$ is balanced at $300\text{cm}$ length of a potentiometer wire. The Potential difference across a resistance in the circuit is balanced at $1.25\text{m}$ . If a voltmeter is connected across the same resistance, it reads $0.65\text{V}$. The error in the voltmeter is (Upto 3 decimal places)_______ $\text{V}$.

Answer 1

From the data given in the question,

$300\times {10}^{-2}\text{m}\to 1.5\text{V}$

$1.25\text{m}\to \text{V}=?$

Thus, $\text{V}=\frac{1.5}{300\times {10}^{-2}}\times 1.25=\frac{1.5}{3}\times 1.25=0.625\text{V}.......\left(1\right)$

Potential difference measured by voltmeter is

${\text{V}}^{\prime }=0.65\text{V}.......\left(2\right)$

Error in the voltmeter is , $\Delta \text{V}=|{\text{V - V}}^{\prime }|$

$=0.625-0.65$

$=0.025\text{V}$