Question

In a moving coil galvanometer the deflection `(phi)` on the scale by a pointer attached to the spring is
A. `((NA)/(kB))I`
B. `((N)/(kAB))I`
C. `((NAB)/(k))I`
D. `((NAB)/(kI))`

Answer 1

Correct Answer - C
Since magnetic torque on the coil, `tau=NIAB`
This torque is balanced by counter torque
`therefore" "kphi=NIAB or phi=((NAB)/(k))I`
where k is torsional constant. It is a scalar quantity having dimension of torque or enegy i.e. `[ML^(2)T^(-2)]`