Question

What is the effect of the ammeter range on the shunt resistance?

(a) no effect

(b) varies by a factor of multiplying factor

(c) varies by a factor of the resistance

(d) varies by a factor of unity

The question was asked in a job interview.

My question is from Shunts and Multipliers in division Extension of Instrument Ranges of Electrical Measurements

Answer 1

Right choice is (b) varies by a factor of multiplying factor

Easy explanation: We know that

N = 1 + ^Ra⁄Rs

where, N is the multiplying factor

       Ra is the ammeter resistance

            Rs is the shunt resistance

It is clear from the above equation that in order to increase the ammeter range by N times, the shunt resistance is equivalent to ^1⁄N-1.