A voltmeter with internal resistance of x can be used to measure upto 20 V. In order to increase its measuring range to 30 V, the required modification is to _____.

Step-by-step solution

Let the maximum current for full-scale deflection of the voltmeter be I_g . I_g = V₁ R_v = 20 x To increase the measuring range to V₂ = 30 V, a resistance R must be connected in series with the voltmeter. V₂ = I_g(R_v + R) 30 = 20 x (x + R) 30x = 20x + 20R 10x = 20R R = x 2 Thus, a resistor of x 2 should be connected in series with the voltmeter. Answer: connect resistor of x 2 , in series with voltmeter.