Question
Download Solution PDFBased on which principle does a Moving Coil meter work?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFPermanent Magnet Moving Coil Instrument (PMMC):
- It works similar to a permanent magnet DC motor with a limited rotation.
- DC motor works on Faradays's Voltage law.
- It is also known as MC (Moving Coil) instrument.
- 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. |
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