CBSE Class 12 · 2023 · Magnetic Effects of CurrentShort Answer

Briefly explain why and how a galvanometer is converted into an ammeter.

Solution

A galvanometer can carry only a tiny current

I_{g}

at full-scale deflection, so it cannot directly measure large currents and, having appreciable resistance, would disturb the circuit. A low shunt resistance

S

is connected in parallel so that it bypasses most of the current:

(I - I_{g}) S = I_{g} G

, giving

S = \frac{I _{g}}{I - I _{g}} G

. The combination has a very low resistance and reads currents up to the chosen range when placed in series.

CBSE Class 12 Board · 2023 · Subjective

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