Question 332 of 380

A galvanometer having coil resistance $10\Omega$ shows a full scale deflection for a current of $3mA$. For it to measure a current of $8A$, the value of the shunt should be:

A$3\times {10}^{-3}\Omega$B$4.85\times {10}^{-3}\Omega$C$3.75\times {10}^{-3}\Omega$D$2.75\times {10}^{-3}\Omega$

Show answer and solution▾

Answer: (C) $3.75\times {10}^{-3}\Omega$

Given $G=10\Omega$, ${I}_{g}=3mA$ and $I=8A$.
Let's consider the following figure:

From the figure, we have
${I}_{g}G=\left(I-{I}_{g}\right)S \Rightarrow S=\dfrac{{I}_{g}G}{I-{I}_{g}} \Rightarrow S=\dfrac{\left(3\times {10}^{-3}\right)10}{8-0.003} =3.75\times {10}^{-3}\Omega$

JEE Main Physics practice question on Current Electricity (Electric Instruments), with the answer and a step-by-step solution. Scan a question from your own book or paper to get a whiteboard video.