Question

A DC ammeter has a resistance of 0.1 Ω and its current range is 0-100 A. If the range is to be extended to 0-500 A, the meter requires which of the following shunt resistance?

(a) 0.010 Ω

(b) 0.011 Ω

(c) 0.025 Ω

(d) 1.0 Ω

I have been asked this question during a job interview.

The query is from Advanced Miscellaneous Problems on Measurement of Resistance in section Measurement of Resistance of Electrical Measurements

Answer 1

The correct option is (c) 0.025 Ω

Easy explanation: Rsh = \( \frac{R_m}{m-1}\)

Where, m is the multiplication factor = 500/100 = 5

∴ Rsh = 0.1/4 = 0.025 Ω.