Question

The full-scale deflection current of an ammeter is 4 mA and its internal resistance is 400Ω. If this meter is to have a full deflection of 10 A, what is the value of the shunt resistance to be used?

(a) 49.99 Ω

(b) 0.16 Ω

(c) 1.5 Ω

(d) 2.6 Ω

I have been asked this question in an online interview.

Asked question is from Advanced Problems on Indicating Instruments in division Extension of Instrument Ranges of Electrical Measurements

Answer 1

The correct option is (b) 0.16 Ω

To explain: Voltage across the meter = 4 × 10^-3 × 4 × 10^2 = 1.6 V

Current through the shunt = 10 – 0.004 = 9.996 A

∴ Shunt resistance = \(\frac{16}{10 × 9.996} \) = 0.16 Ω.