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# Generators: Principle and Working

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Generators

How does it work?

How does it apply or use magnetism?

Which basic equation(s) govern its operation?

Does this device have historical significance? If so, what is it?

What do you envision as the future of this device?

Can you imagine any other applications of the device?

https://brainmass.com/physics/ac/generators-principle-working-199331

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What device did you choose?
Motors/Generators
Generator

How does it work?
A generator is a device converts mechanical energy in to electric energy. It works on the principle of electromagnetic induction. When a coil of insulated wire is rotated in a magnetic field, an electromotive force is induced in it and because of this a current called induced current will flow through the electrical appliance connected with the terminals of the coil. The terminals of rotating coils are connected to external appliance through connecting brushes using slipping contacts.
How does it apply or use magnetism?
It uses permanent magnets creating magnetic field, due to this field because of electromagnetic interaction induced current will flow through the rotating coil. According to Lenz law the direction of induced current is such that it opposes the cause by which it produced. Here the induced current is produced due to rotation of coil and hence rotation of the coil is opposed and hence to rotate it we have to do the work. This work done to rotate coil appears in form of electrical energy. The magnetic field or its energy is not consumed but the presence of magnetic field is essential.
Which basic equation(s) govern its operation?
The basic principle for generators is the Faraday's laws of electromagnetic induction.
1. When magnetic flux through a closed loop changes, an induced EMF is develops in the loop due to this induced current flows through it. This phenomenon is called Electromagnetic induction.
2. The induced EMF in the loop is directly proportional to the rate of change of magnetic flux through it.
From second law induced EMF e is given by

Now consider a loop of area A rotated in a magnetic field B with angular velocity  as shown in figure.
The magnetic flux through the area is given by

where  is the angle between the surface vector and the magnetic field.
The initial angle is 900. The angle turned by the loop in time t is t hence the angle between the area vector and the field at time t is 900 + t
Hence the magnetic flux through the loop as a function of time t is given by

Hence the induced EMF is given by faraday's law as

hence the induced EMF is a function of time and given by

e =  BA cos (t)
this EMF will alternate with time and hence the current through it is called alternating current.
Does this device have historical significance? If so, what is it?

What do you envision as the future of this device?
Hans Christian Oersted discovered that a current carrying conductor produces magnetic field. Michel Faraday thought that the reverse should be possible, means the magnetic field may produce electric current. After many years of try he showed his experiment for this in 1831. In this experiment a coil is connected to a galvanometer and a magnet is inserted in the coil. During the motion of magnet the galvanometer registered a current.
From here the phenomenon of electromagnetic induction developed and step by step the development of generator took place.
Hippolyte Pixii invented a hand-driven generator in 1832 in which the magnet revolved and the conductor (coils) remained stationary.
Ampere (1775-1836) suggested using a commutator to change alternating current to direct current.
In 1846 Ernst Werner von Siemens devised a generator that did not need permanent magnets. His dynamo-electric principle used self-generated electricity to activate electromagnets.

Can you imagine any other applications of the device?
If in the coil of generator a current is passed it will rotate the coil and the generator may convert to electric motor.

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