Based on which principle does a Moving Coil meter work?

Question

Question

This question was previously asked in

ALP CBT 2 Electronic Mechanic Previous Paper: Held on 21 Jan 2019 Shift 2

Answer 1

Permanent Magnet Moving Coil Instrument (PMMC):

F2 Shubham 28.10.20 Pallavi D2

The coil rotates between the magnetic field of the permanent magnet for measuring the DC quantities
It works on the principle that the force acting on the coil places between the magnetic field of the permanent magnet.
And because of this magnetic field, the coil rotates.

Faraday's Voltage law:

The Induced voltage in a circuit is proportional to the rate of change over time of the magnetic flux through that circuit.

In MC instrument,

The induced emf in a coil is equal to the negative of the rate of change of magnetic flux times the number of turns in the coil.

Moving coil galvanometer is an electromagnetic device that can measure small values of current.
It works on the principle that when a current loop is placed in an external magnetic field, it experiences torque, and
The value of torque can be changed by changing the current in the loop

Points to remember:

Moving Iron Instrument	Moving Coil Instrument
It uses the soft iron piece as a rotating element.	It uses the coil as a rotating element.
The MI iron instrument has a non-uniform scale.	The moving coil instrument has a uniform sale.
MI instrument is less accurate	PMMC is more accurate
It uses the air friction damping	It uses the eddy current damping system.
It is used for measuring both the direct and alternating current	It is used for the DC measurement
The gravity or spring provides the controlling torque to the instrument.	The spring provides the controlling torque to the moving coil instrument.
The moving iron instrument can be used as an ammeter, voltmeter, and wattmeter.	the moving coil instrument is used as a voltmeter, ammeter, galvanometer, and ammeter.
It measures the RMS value of quantity and the deflection is directly proportional to the square of the current.	It measures the average value of quantity and the deflection is directly proportional to the current.