CBSE Class 12 · 2005 · All India · Magnetic Effects of CurrentShort Answer

How do you convert a galvanometer into an ammeter? Why is an ammeter always connected in series?

Solution

A galvanometer gives full-scale deflection for a tiny current

I_{g}

. To read a larger current

I

, a low shunt resistance

S

is joined in parallel so that it carries

(I - I_{g})

while the coil carries only

I_{g}

(I - I_{g}) S = I_{g} G \Rightarrow S = \frac{I _{g}}{I - I _{g}} G .

The combination has a very small resistance and is placed in series with the circuit, so the full current flows through it without appreciably changing that current.

CBSE Class 12 Board · 2005 · All India · Subjective

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