Question
If the current is doubled, the deflection is also doubled in:
  1. A tangent galvanometer.
  2. A moving-coil galvanometer.
  3. Both.
  4. None.

Answer

  1. A moving-coil galvanometer.

Explanation:

The current and deflection dependence of a moving coil galvanometer is given by

$\text{i}=\frac{\text{k}}{\text{nAB}}\theta\Rightarrow\text{i}\propto\theta$

Therefore, if we double the current, the deflection also gets doubled.

However, in a tangent galvanometer, $\text{i}\propto\tan\theta$; that is, there is no direct relation between $\theta$ and current.

Hence, the correct option is (b).

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