A galvanometer can be converted into an ammeter of desired range by connecting a:
Show Hint
- small resistance in series
- large resistance in series
- small resistance in parallel
- large resistance in parallel
The Correct Option is C
Solution and Explanation
Top Questions on The Moving Coil Galvanometer
- With the help of a labelled diagram, explain the principle of working of a moving coil galvanometer. Write the purpose of using (i) radial magnetic field, and (ii) soft iron core, in it.
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Assertion (A): The deflection in a galvanometer is directly proportional to the current passing through it.
Reason (R): The coil of a galvanometer is suspended in a uniform radial magnetic field.
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- In a moving coil galvanometer, two moving coils $ M_1 $ and $ M_2 $ have the following particulars: $ R_1 = 5 \, \Omega $, $ N_1 = 15 $, $ A_1 = 3.6 \times 10^{-3} \, \text{m}^2 $, $ B_1 = 0.25 \, \text{T} $ $ R_2 = 7 \, \Omega $, $ N_2 = 21 $, $ A_2 = 1.8 \times 10^{-3} \, \text{m}^2 $, $ B_2 = 0.50 \, \text{T} $ Assuming that torsional constant of the springs are same for both coils, what will be the ratio of voltage sensitivity of $ M_1 $ and $ M_2 $?
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- Consider a moving coil galvanometer (MCG):
A : The torsional constant in moving coil galvanometer has dimensions \( [ML^2 T^{-2}] \)
B : Increasing the current sensitivity may not necessarily increase the voltage sensitivity.
C : If we increase the number of turns (N) to its double (2N), then the voltage sensitivity doubles.
D : MCG can be converted into an ammeter by introducing a shunt resistance of large value in parallel with the galvanometer.
E : Current sensitivity of MCG depends inversely on the number of turns of the coil.
Choose the correct answer from the options given below:- JEE Main - 2025
- Physics
- The Moving Coil Galvanometer
Galvanometer:
A galvanometer is an instrument used to show the direction and strength of the current passing through it. In a galvanometer, a coil placed in a magnetic field experiences a torque and hence gets deflected when a current passes through it.
The name "galvanometer" is derived from the surname of Italian scientist Luigi Galvani, who in 1791 discovered that electric current makes a dead frog’s leg jerk.
A spring attached to the coil provides a counter torque. In equilibrium, the deflecting torque is balanced by the restoring torque of the spring, and we have the relation:
\[ NBAI = k\phi \]
Where:
- \( N \) is the total number of turns in the coil
- \( A \) is the area of cross-section of each turn
- \( B \) is the radial magnetic field
- \( k \) is the torsional constant of the spring
- \( \phi \) is the angular deflection of the coil
As the current \( I_g \) that produces full-scale deflection in the galvanometer is very small, the galvanometer alone cannot be used to measure current in electric circuits.
To convert a galvanometer into an ammeter (to measure larger currents), a small resistance called a shunt is connected in parallel to the galvanometer.
To convert it into a voltmeter (to measure potential difference), a high resistance is connected in series with the galvanometer.
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