Q 12-04-042JEE MainJEE Main 2026 (4 Apr, Shift 1)Easy
A voltmeter with internal resistance of $x\,\Omega$ can be used to measure upto $20$ V. In order to increase its measuring range to $30$ V, the required modification is to ______.
Answer: (A) connect resistor of $\dfrac{x}{2}\,\Omega$, in series with voltmeter.
Concept. A voltmeter's full-scale current is fixed: $I=\dfrac{20}{x}$. For $30$ V the total resistance must be $\dfrac{30}{I}=1.5x$.
Step 1. Extra. $1.5x-x=\dfrac x2$ in series.
Answer. Option A.
Solution by Sreeraj P, M.Sc Physics
