Generators

Generators

Motors are devices that use electricity to create motion.

Generators are devices that use the motion of something to produce electricity. There’s a small kind of generator that’s familiar to almost every one of you, the dynamo fitted over the front wheel of your cycle.

Small generator/Dynamo

Fig:- Sorry that I couldn’t draw that thing accurately, but this picture is available in the web and those of you who have the book, see page 192.

An example of a small generator is the dynamo. Usually we use dynamo in the bicycle or in the different motor vehicles.

When a cyclist paddles, the wheels rotate. When wheels rotate, magnet inside the dynamo spins. It produces magnetic flux linkage cut. An induced emf is produced across the coil.

*[The dynamo is a small generator, so we’re using a small and a less stronger magnet that can rotate. But in large scale electricity generator, we can’t make so big magnets rotate. That’s why we place two of the magnets of North and South poles a little apart and in between of them we let rotate the coil, producing voltage.]

*[Big, large scale generators are called alternators.]

Alternator

A generator that produces A.C. is known as alternator.

In alternator, coil rotates between two magnets. This rotation produces magnetic flux linkage cut and an induced voltage is produced across the coil. We use slip ring to make complete rotation. Frequency of the alternating current depends on the number of rotation of the coil in one second. If an alternator rotates twice in a second, the frequency of the alternating current it produces is 2Hz (2 cycles per second).

Transformers

A transformer is a device which can transfer voltage by using the principle of electromagnetic induction (you’ll come to know about this principle in details at A’ Level).

Fig:- This is a diagram of the inside of a transformer.

*[You will see many transformers at your living area on the roads and streets.]

There are two coils in the transformer. One is primary coil and another is secondary coil. Input signal(current) is connected in the primary coil (input signal must be an alternating current). There is a flux linkage change due to the alternating current. This change in flux linkage cut in the secondary coil. This flux linkage cut produces induced emf in the secondary coil. There are 2 types of transformers.

1. Step up:- If output voltage is larger than input voltage, that transformer is known as step up transformer.
2. Step down:- If output voltage is smaller than input voltage, that transformer is know as step down transformer.