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What is the resistance of R1

  • #1
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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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Answers and Replies

  • #2
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is there anything wrong with my work ?
 

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