Question:

If only 151th\frac{1}{51}^{th} ot the main current is to be passed through a galvanometer then the shunt required is R1R_1 and if only 111th\frac{1}{11}^{th} of the main voltage is to be developed across the galvanometer, then the resistance required is R2R_2. Then R2R1=\frac{R_2}{R_1} =

Updated On: Apr 4, 2024
  • 1500\frac{1}{500}
  • 509\frac{50}{9}
  • 5003\frac{500}{3}
  • 500500
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The Correct Option is D

Solution and Explanation

According to the question,



If only 151\frac{1}{51} th of the main current ii is to be passed through galvanometer GG then the shunt required is main current, i=51i=51
ig=1 i_{g}=1
R1=Gii9 \therefore R_{1}=\frac{G}{i-i_{9}}
R1=G511=G50     ....(i)\Rightarrow R_{1}=\frac{G}{51-1}=\frac{G}{50} \,\,\,\,\,....(i)



If only 111th\frac{1}{11} th of the main voltage is developed across the GG then the resistance required, R2R_{2}.
R2=G(VG1)R_{2}=G\left(V_{G}-1\right)
R2=G(111)=10G        (ii)R_{2}=G(11-1)=10 G\,\,\,\,\,\,\,\,\dots(ii)
Now, from Eqn. (i) and (ii), we get
R2R1=10GG50=500\frac{R_{2}}{R_{1}}=\frac{10 G}{\frac{G}{50}}=500
R2R1=500\therefore \frac{R_{2}}{R_{1}}=500
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Concepts Used:

Electrical Instruments

There are various electrical instruments used to measure current, power, voltage, etc.  Some of them are briefly explained below:

Moving Coil Galvanometer

  • It is an electromagnetic device which measures small values of current.
  • Its working principle is that whenever a current loop is placed in a magnetic field, it experiences a certain torque. The value of that torque can be modified by modifying the current in the loop.
  • For a current carrying loop having N turns, and cross sectional area A, carrying current i, whenever it is placed in and along the direction of an external magnetic field B, it experiences a torque given by:

ԏ = NiAB

moving coil galvanometer