A moving coil galvanometer of resistance 100 shows a full scale deflection for a current of 1 mA. The value of resistance required to convert this galvanometer into an ammeter, showing full scale deflection for a

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Quantrex Academy · Accepted Answer

Correct answer: D. 25

To convert a galvanometer to an ammeter, a shunt resistance

S

is connected in parallel. For full-scale deflection:
Current through galvanometer:

I_g = 1

mA
Total current:

I = 5

mA
Current through shunt:

I_s = 5 - 1 = 4

mA
Since voltage across both is equal:

I_g \cdot G = I_s \cdot S

0.001 \times 100 = 0.004 \times S

S = \frac{0.1}{0.004} = 25

Ω

A moving coil galvanometer of resistance 100 shows a full scale...

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