Name: Electric Field: Time Varying Magnetic Field
Uploaded: 2019-07-19
Duration: 8 min 32 s
Description: Did you know that the cause of the movement of charges in a stationary circular conducting coil placed in a time-varying magnetic field is due to an induced...

Question

Describe with neat and suitable diagram, the construction and working of

A C

generator. Derive the expression of the

e m f

used.

Accepted Answer

AC generator is a machine that converts mechanical energy into electrical energy. The AC Generator’s input supply is mechanical energy supplied by steam turbines, gas turbines and combustion engines. The output is alternating electrical power in the form of alternating voltage and current.

AC generators work on the principle of Faraday’s law of electromagnetic induction, which states that electromotive force, EMF or voltage is generated in a current-carrying conductor that cuts a uniform magnetic field. This can either be achieved by rotating a conducting coil in a static magnetic field or rotating the magnetic field containing the stationary conductor. The preferred arrangement is to keep the coil stationary because it is easier to draw induced alternating current from a stationary armature coil than a rotating coil.

The generated EMF depends on the number of armature coil turns, magnetic field strength, and the speed of the rotating field.

AC Generator Parts and Function:

The various parts of an AC generator are:

Field: The field consists of coils of conductors that receive a voltage from the source and produce magnetic flux. The magnetic flux in the field cuts the armature to produce a voltage. This voltage is the output voltage of the AC generator.

Armature: The part of an AC generator in which the voltage is produced is known as an armature. This component primarily consists of coils of wire that are large enough to carry the full-load current of the generator.

Prime Mover: The component used to drive the AC generator is known as a prime mover. The prime mover could either be a diesel engine, a steam turbine, or a motor.

Rotor: The rotating component of the generator is known as a rotor. The generator’s prime mover drives the rotor.

Stator: The stator is the stationary part of an AC generator. The stator core comprises a lamination of steel alloys or magnetic iron to minimise the eddy current losses.

Slip Rings: Slip rings are electrical connections used to transfer power to and fro from the rotor of an AC generator. They are typically designed to conduct the flow of current from a stationary device to a rotating one.

Working of an AC Generator:

When the armature rotates between the poles of the magnet upon an axis perpendicular to the magnetic field, the flux linkage of the armature changes continuously. As a result, an electric current flows through the galvanometer and the slip rings and brushes. The galvanometer swings between positive and negative values. This indicates that there is an alternating current flowing through the galvanometer. The direction of the induced current can be identified using Fleming’s Right-hand Rule.

The expression for instantaneous value of induced emf:

When a coil is rotated with a constant angular speed $ω$ , the angle $θ$ between the magnetic field vector $B$ and the area vector $A$ , of the coil at any instant $t$ equals $ωt$ , assuming $θ = 0 °$ at $t = 0$ As a result, the effective area of the coil exposed to the magnetic field changes with time. The flux at any instant $t$ is given by,

$ϕ_{B} = NBA cosθ = NBA cosωt$

The induced emf, $ε = - N \frac{dϕ}{dt} \Rightarrow ε = - NBA \frac{dϕ}{dt} (cosωt) \Rightarrow ε = NBAωsinωt$ .

Describe with neat and suitable diagram, the construction and working of $A C$ generator. Derive the expression of the $e m f$ used.

Important Questions on Electromagnetic Induction

Learn and Prepare for any exam you want !

Describe with neat and suitable diagram, the construction and working of AC generator. Derive the expression of the emf used.

Important Questions on Electromagnetic Induction

Learn and Prepare for any exam you want !

Describe with neat and suitable diagram, the construction and working of $A C$ generator. Derive the expression of the $e m f$ used.