The figure shows a dual range dc milliammeter which has a common negative terminal A and positive terminal B and C . The indiacator is a moving coil meter of resistance 50 ohm which gives full scale deflectino with a current of 1.0 mA . When connection ismade with the terminals A and C , a current of 20 mA gives full scale deflection . What is the resistance of R1 ?
The Attempt at a Solution
when A and B are connected to a circuit , R1+R2=50 ohm
when A and C are connected to a circuit ,
1mA will flow through the resistor R2 , then to the meter while 19 mA will flow through resistor R1 .
and pd across meter = pd across shunt
and R1=0 ??
Cant be !