Q. A voltmeter having a resistance of $998\ ohm$ is connected to a cell of e.m.f. $2\ volt$ and internal resistance $2\ ohm.$ The error in the measurement of e.m.f. will be
A) $4 \times 10^{- 1}volt$
B) $2 \times 10^{- 3}volt$
C) $4 \times 10^{- 3}\ volt$
D) $2 \times 10^{- 1}\ volt$
Explanation
(c) Error in measurement = Actual value – Measured value
Actual value $= 2V$
$i = \frac{2}{998 + 2}$
$= \frac{1}{500}A$
Since $E = V + ir$
$\Rightarrow V = E - ir = 2 - \frac{1}{500} \times 2 = \frac{998}{500}V$
$\therefore$ Measured value $= \frac{998}{500}V$
$\Rightarrow$ Error $= 2 - \frac{998}{500} = 4 \times 10^{- 3}volt$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.