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MHT CET · Physics · Current Electricity

An ammeter of resistance ' \(R\) ' gives a full scale deflection when a current of 2 A passes through it. If it is to be converted into an ammeter to measure maximum current of \(10 \mathrm{~A}\), the required shunt is

  1. A \(\frac{\mathrm{R}}{2}\)
  2. B \(\frac{\mathrm{R}}{4}\)
  3. C \(2 \mathrm{R}\)
  4. D R
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{\mathrm{R}}{4}\)

Step-by-step Solution

Detailed explanation

Consider the diagram below:

Given, \(\mathrm{i}_{\mathrm{g}}=2 \mathrm{~A}\) is current for maximum deflection, \(\mathrm{R}=\mathrm{R}_{\mathrm{g}}\) is the resistance of galvanometer, \(\mathrm{I}=10 \mathrm{~A}\) is the maximum current to be measured by the ammeter.
On considering same potential drop across the galvanometer and the shunt resistance:
\(\Rightarrow\left(I-i_g\right) S=i_g R\).
On plugging in the given values,
\((10 A-2 A) S=(2 A) R\)
The shunt resistance \(S\) can be written as: \(S=\frac{R}{4}\)