A galvanometer with coil resistance 100 ohm shows full-scale deflection when 1 mA flows through it. What shunt resistance, placed across it, will turn it into an ammeter that reads full scale at 10 A?

3 ohm
0.01 ohm
2 ohm
0.1 ohm

Correct answer: 0.01 ohm

Solution

The shunt carries (I - Ig) and shares the same potential difference as the galvanometer coil. Solving gives a very small shunt of about 0.01 ohm.

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