Transformers

Class: 12

Submitted to:

Mr. Jonny beaver,

Physics teacher

Submitted by:

Mohammed Al Khabori

19 February 2011

Theoretical report

Transformers

I have generated series of questions, regarding the transformers, which are to be researched and answered. They are the following: * What is the history of transformers?

* What is a transformer?

* Which principle/laws does the transformer obey?

* How can we construct a transformer?

* How does a transformer function/work?

* What are the mathematical formulae, which show the relationship between the different quantities to be measured and how it’s derived?

* What are the different types of transformers?

* What is the major source of energy loss in a transformer? * What are the uses of transformers?

* Why do we employ high voltages?

History of transformers:

Transformer is based upon the theory of electromagnetic induction and Michael Faraday discovered that in 1831. In 1836 the first device, an induction coil, was invented. William Stanley, who designed the first commercial model, introduced the term "transformer" in 1885. What is a transformer?

Transformers are electrical devices that change the value of an alternating voltage.They do this by applying the principle of magnetic induction between coils to convert voltage and/or current levels. Transformers are mainly made up of two coils wrapped around the iron core. The first coil is called the primary coil and the second coil is called the secondary coil. What principle/law does the transformer obey?

The transformer obeys the faradays law. Faradays law states that the size of the induced voltage in a conductor equals the rate of change of magnetic flux. How can we construct a transformer?

Transformers are mainly composed of iron core made of laminated sheets, well insulated from one another. The iron core normally comes in a rectangular shape. There are two coils (P1&P2) wrapped around on the iron core. Both of the coils are well insulated from the core. The first coil is called the primary coil and the second coil is called the secondary.The A.C current in the primary coil induces a magnetic flux that flows around the iron core. The magnetic flux in the core induces an alternating current in the secondary coil. The voltage in the secondary coils is directly proportional to the number of turns in the primary coil divided by the number turns in the secondary coil. The formula is: Vs/Vp=Ns/Np. Here is an image of how a transformer looks like:

How does a transformer function/work?

Alternating current is passed through the primary coil, which creates a changing magnetic field in the iron core. The changing magnetic field then induces alternating current of the same frequency in the secondary coil (the output). There are four ways that flux can be changed: Moving coil: the coil is moved but the magnet remains stationary. Moving magnet: the magnet is moved but the coil remains stationary. Changing the area: both the magnet and the coil remain stationary but the area is changed. Mutual induction: all three magnets, coil and area remain stationary only flux is changed with the help of changing currents, thus transformers work only under A.C. and not D.C. So the change of flux is achieved by the mutual induction. In a transformer the method mutual induction is used.

Here is an example of how transformers function in power stations:

1.Fuel is burnt, which causes the water to heat

2.When water is heated it starts to boils therefore steam is produced 3.The turbines then turn

4.Generators are turned which then produces electricity

5.Transformers modify the voltage

What are the mathematical formulae, which shows the relationship between different quantities to be measured and how are they derived? According to faraday’s law, the size of the induced voltage in a conductor equals the rate of change of magnetic flux. If I were to...