Question

Pick out the expression for galvanometer constant from the following?

(a) G = \(\frac {k}{NAB}\)

(b) G = k × NAB

(c) G = \(\frac {NAB}{k}\)

(d) \(\frac {1}{G} \, = \, \frac {k}{NAB}\)

I have been asked this question during an interview.

Origin of the question is Moving Coil Galvanometer topic in portion Moving Charges and Magnetism of Physics – Class 12

Answer 1

Right option is (a) G = \(\frac {k}{NAB}\)

For explanation: In a moving coil galvanometer, the current (I) passing through the galvanometer is directly proportional to its deflection (θ), i.e.

I = Gθ

Where G = \(\frac {k}{NAB}\) ➔ Galvanometer constant

 N = number of turns in the coil; A = area of coil; B = strength of the magnetic field; k = torsional constant of the spring that means restoring torque per unit twist.