What is the Resistance of R1 in a Dual Range DC Milliammeter?

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The discussion revolves around calculating the resistance of R1 in a dual range DC milliammeter setup. The meter has a moving coil with a resistance of 50 ohms, indicating full scale deflection at 1.0 mA, while a connection at terminals A and C allows for 20 mA to achieve full scale deflection. The equations derived indicate that R1 and R2 must sum to 50 ohms, but an attempt to solve leads to an incorrect conclusion that R1 equals zero. Participants are questioning the validity of the calculations and seeking clarification on potential errors in their approach. The conversation highlights the complexity of analyzing circuit configurations in milliammeter applications.
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Homework Statement



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 ?

Homework Equations





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

1(50)=19R1+R2 ---1

R1+R2=50 ----2

and R1=0 ??

Cant be !
 

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