A millivoltmeter of range `0-50` mV and resistance `50Omega` is to be converted into an ammeter of range `0-1A`. How much it be done ?

Explanation

Resistance of the millivolmeter `R=50 Omega`, maximum voltange `V=50mV=0.05V`.
Connecting a shunt s in parallel with the millivolmeter and using this combination in between the points A and B [Fig. 1.81], we shall get an ammeter to measure a maximum current I. Here `I=IA`.
Now, `I_(S)*S=I_(v)*R`
or, `S=(I_(V))/(I_(S))*R=(I_(V))/(I-I_(V))*R`
`=((V)/(R))/(I-(V)/(R))*R=(V)/(I-(V)/(R))=(0.05)/(1-(0.05)/(50))=(0.5)/(1-0.001)=0.05Omega`

This is the required value of the shunt-resistance.