Physics, asked by jaydeepthakur841, 1 year ago

A galvanometer can be converted into a voltmeter to measure upto:

(i) 'V' volts by connecting a resistance R1 in series with coil.

(ii) 'v/2' volts by connecting a resistance R2 in series with coil.

Find the resistance (R) in terms of R1 and R2 required to convert it into a voltmeter that can read upto '2V' volts.

Answers

Answered by prabhas24480
1

According to the formula, R = V/Ig – G where V is the potential difference across the terminals of the voltmeter

Ig is the current in the galvanometer

G is the resistance of the galvanometer

Case 1: Resistance R1 is connected to measure voltage V

Hence, R1 = V /Ig – G ----------------Eqn (1)

Case 2: Resistance R2 is connected to measure voltage V/2

Hence, R2 = (V/2) /Ig – G --------------Eqn (2)

Eqn (1) – Eqn (2) gives R1 – R2 = 1/Ig (V-V/2) = V/2Ig

As V/2Ig = R1 – R2 substitute in Eqn (2), we get R2 = R1 – R2 – G Hence, G = R1 – 2R2

This is G in terms of R1 and R2

Case 3: Resistance R3 is connected to measure voltage 2V

Hence, R3 = (2V) /Ig – G --------------Eqn (3)

= 4(R1 – R2) – (R1 – 2R2) = 3R1 – 2R2

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