Question

on what principle moving coil galvanometer works?

Answer 1

it works on the principle that when current carrying coil kept in a magnetic field , coil experiences torque due to which coil starts rotating...

Torque , T = MBSin@
where ,
M = Magnetic moment = I A
( I = Current , A = Area vector )
B = Intensity of Magnetic field
@ = angle between M and A

Here magnetic field is radial magnetic field which is created by using U-Shape magnet...By taking such magnetic field , Torque on a coil become indepenedent of Angle between the M ( magnetic moemnt ) and B ( Magnetic field )...i e , Angle is 90 degree...ie, @ = 90 degree...

Torque experience by coil will be
T = MBSin90
= MB ( Sin90 = 1 )

Answer 2

Explanation:

The moving coil galvanometer working principle is based upon the fact that when electric current flows in a coil placed in a magnetic field, a deflecting torque acts upon the coil whose magnitude depends upon the strength of the current.

From the measurement of the deflection of the coil, the strength of the current can be computed.

Moving-coil galvanometers are of two types:

Suspended coil galvanometer and,

Pivoted-coil or Weston galvanometer.

The principle and working of the two types of galvanometers are the same, only there is some difference in their constructions.

In a suspended coil galvanometer, the coil is suspended by a thin phosphor bronze strip and the deflection of the coil is measured by a lamp and a scale arrangement. A suspended coil galvanometer can measure currents of the order of 10-9 A.