Name: Purely Inductive Circuit
Uploaded: 2019-07-19
Duration: 5 min 40 s
Description: How does an inductor behave in a circuit? This video will explain every parameter involved in the derivation of a pure inductor working with AC supply.

Question

What is a transformer? Describe the principle, construction and working method of a transformer.

Accepted Answer

The transformer is a device that transfers electric energy from one alternating-current circuit to one or more other circuits, either increasing (step up) or reducing (step down) the voltage.

Principle behind the working of transformer: It works on the principle of mutual induction that is, if two coils are inductively coupled then on the flow of an alternating current in one coil an alternating induced emf is also produced in the other coil.

Construction of transformer:

Transformer consists of two coils, a primary coil $P$ and a secondary coil $S$ , wound on a laminated soft iron core. Alternating current input supply is connected to the primary coil and the output voltage is obtained across a load joined in secondary coil circuit.
Depending upon the output of the transformer, the transformer is of the following two types:
(i) Step-up transformer, in which the number of turns in secondary coil is more than in primary coil, to obtain a higher alternating output voltage.
(ii) Step down transformer, in which the number of turns in secondary coil is less than primary coil, to obtain a lower alternating output voltage.

Working of Transformer:

When an alternating electromotive force source is applied across the primary coil, it generates input current in the primary coil that is referred as primary current, as a result the primary coil generates magnetic flux. As the input source is an a.c. source thus the direction of flux generated by the coil keeps on changing with time. The changing magnetic flux gets linked up with secondary coil through the iron core, which result in secondary current and induces output voltage across the secondary coil.

The induced emf in $P$ coil is : $E_{p} = - N_{P} \frac{d ϕ_{B}}{d t}$ , here $N_{P}$ is number of turns in primary coil.

Thus, the instantaneous value of induced emf in secondary coil is: $E_{S} = - N_{S} \frac{d ϕ_{B}}{d t}$ , here $N_{S}$ is number of turns in secondary coil.

Here, $ϕ_{B}$ is the magnetic flux linked with both the coils.

From the above two relation we can conclude that voltage across the coils is directly proportional to number of turns present in the coil.

What is a transformer? Describe the principle, construction and working method of a transformer.

Important Questions on Alternating Current

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