Question

An ammeter has a resistance of 0.04 ohms and reads 2A per scale division. what shunt will cause it to read 10mA per scale division

Answer 1

Ia+Is = 2A.

0.01+Is = 2
Is = 1.99A = Current through shunt.
Vs = Va = Ia*Ra = 0.01*0.04 = 4*10^-4 volts.
Rs = Vs/Is = 4*10^-4/1.99 = 2.01*10^-4 ohms = 0.201 milliohms.