A voltmeter with internal resistance of x Ω can be used to measure upto 20 V. In order to increase its measuring range to 30 V, the required modification is to ______. (a) connect resistor of x/2 Ω, in series with voltmeter. (b) connect resistor of x/2 Ω, in parallel to voltmeter. (c) connect a resistor of x Ω in series with voltmeter. (d) connect resistor of 2x Ω in parallel to voltmeter.

Answer: (a). To raise a voltmeter's range a resistance is added in series: R = RV(V'/V - 1). R = x(30/20 - 1) = x/2 Ω So the answer is (a) x/2 Ω in series.

A voltmeter with internal resistance of x Ω can be used to measure… | JEE Main 2026 (4 Apr, Shift 1)

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Kirchhoff's Laws & Measuring Instruments

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 ______.

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Answer: (a)

To raise a voltmeter's range a resistance is added in series: $R = R_V\left(\frac{V'}{V} - 1\right)$ .
$R = x\left(\frac{30}{20} - 1\right) = \frac{x}{2}\ \Omega$
So the answer is (a) $\frac{x}{2}\ \Omega$ in series.

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