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Explain the working of AC genertor,DC genertor,Moving coil Micrcophone,Moving coil Loud speaker?
DC generator
A D.C. generator works upon the principle of Electromagnetic induction that includes both Faraday's laws and Lenz's law.
To understand the working of a D.C. Generator,it is logical to get first get a brief idea of its construction part.
The D.C. generator(or any D.C. machine) has the following parts:
Stationary members(Stator)
Stator frame
Stator core
Field windings
Brushes

Rotary members(Rotor):
Armature core
Armature windings
Bearings

Now,the working of the generator can be explained as:
The field windings are provided with a current so as to develop a magnetic field around the armature(rotor) of the generator.This phenomenon is also known as field Excitation.
When the armature is made to rotate with the help of any prime mover in the magnetic field as generated by the stator side,an emf is induced in the armature.The magnitude of this generated emf is given by Faraday's law while the direction is given by Lenz's law.
When the armature windings are connected to any load,an electric current begins to flow.
In this way,a DC generator works.

AC Generator
AC generators work on the principle of electromagnetic induction. This phenomenon takes place when conductor coils spin in a magnetic field inducing a current and a voltage.

As in the DC motor case, a current is passed through the coil, generating a torque on the coil. Since the current is alternating, the motor will run smoothly only at the frequency of the sine wave. It is called a synchronous motor. More common is the induction motor, where electric current is induced in the rotating coils rather than supplied to them directly.

One of the drawbacks of this kind of AC motor is the high current which must flow through the rotating contacts. Sparking and heating at those contacts can waste energy and shorten the lifetime of the motor. In common AC motors the magnetic field is produced by an electromagnet powered by the same AC voltage as the motor coil. The coils which produce the magnetic field are sometimes referred to as the "stator", while the coils and the solid core which rotates is called the "armature". In an AC motor the magnetic field is sinusoidally varying, just as the current in the coil varies. 

Moving coil Microphone

A moving coil microphone works by suspending a coil of wire on a diaphragm in the field of a magnet. When sound waves interact with the diaphragm, the coil vibrates, inducing an electric current in the coil, which is sensed by the mixer/amplifier.The electric microphone is a special type of condenser microphone. A moving diaphragm and a fixed back plate form a parallel-plate capacitor, which is charged with a DC voltage. The sound waves hitting the microphone make the diaphragm vibrate. As a result, the capacitance varies, which causes voltage variations across the resistor that are proportional to the incident sound signal.

Moving coil Loud speaker

A loudspeaker produces sound by converting electrical signals from an audio amplifier into mechanical motion. Sound is created from the forward and backward motion of the loudspeaker cone, which is a concave plastic or paper disc. The cone is mounted and centered on a concave metal frame by a ring of flexible rubber. Glued to the centre of the cone is a hollow cylinder of thin, lightweight aluminium. A length of thin, insulated wire is wound upon the bobbin to form the voice coil; both ends of the voice coil wire are connected to the voice coil terminals on the frame. The voice coil is positioned inside a narrow cylindrical groove or air gap in the centre of a magnet. The coil is suspended in the air gap by a flexible fabric disc. An audio amplifier is connected to the voice coil terminals. The coil emits a magnetic field as audio signals from the amplifier travel through the voice coil wire. The voice coil field alternately pulls and pushes the coil, bobbin and cone assembly towards and against the magnetic field from the magnet, which causes the forward and backward cone motion.


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