A galvanometer with a coil resistance of 40.0 Ω deflects full scale for a current of 2.0 mA. What series resistance should be used with this galvanometer in order to construct a voltmeter that deflects full scale for 50 V?
A)25 kΩ
B)27 kΩ
C)29 kΩ
D)31 kΩ
E)35 kΩ

Question

Quizplus · Accepted Answer

To convert the galvanometer into a voltmeter that reads full scale at 50 V, we need to calculate the series resistance required. The full-scale current is 2.0 mA, and the coil resistance is 40 Ω. Using Ohm's law (V = IR), the total resistance needed is 50 V / 0.002 A = 25,000 Ω. Subtracting the coil resistance (40 Ω) from this gives the series resistance: 25,000 Ω - 40 Ω = 24,960 Ω, which is approximately 25 kΩ.

A Galvanometer with a Coil Resistance of 40