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

Describe a transformer on the basis of the following points : Working method and principle

Accepted Answer

Principle: A transformer works on the principle of mutual induction. A transformer consist of two coils, they are primary coil and secondary coil. When flux linked with primary coil changes, it induces emf in the secondary coil. A transformer is used to increase or decrease the alternating voltage.

It consists of two coils, primary $(P)$ and secondary $(S)$ insulated from each other and wound on a soft iron core as shown in the figure. Primary coil is called input coil and secondary coil is called output coil. When an alternating voltage is applied to the primary coil, the current through the coil goes on changing. Hence, the magnetic flux through the core also changes. As this changing magnetic flux is linked with both the coils, an e.m.f. is induced in each coil. The amount of the magnetic flux linked with the coil depends upon the number of turns of the coil.

Let $ϕ$ be the magnetic flux linked per turn with both the coils at a certain instant $t$ , and let $N_{p}$ and $N_{s}$ 'be the number of turns of primary and secondary coil, respectively.

The induced e.m.f. in each turn is given by, $e_{t} = - \frac{d ϕ}{d t}$ .
Hence, the induced e.m.f in the primary coil is given by, $e_{p} = - N_{p} \frac{d ϕ}{d t}$ and the induced e.m.f in the primary coil is given by, $e_{s} = - N_{s} \frac{d ϕ}{d t}$
Using these equations, $\frac{e_{s}}{e_{p}} = \frac{N_{s}}{N_{p}}$ .

This is called the equation of transformer, and the ratio $\frac{N_{s}}{N_{p}}$ is called turns ratio (transformer ratio). For an ideal transformer, the input power must be same as the output power.

Hence, $e_{p} i_{p} = e_{s} i_{s}$

where $i_{p}, i_{s}$ are the currents in primary and secondary coils respectively.

$\Rightarrow \frac{i_{p}}{i_{s}} = \frac{e_{s}}{e_{p}} = \frac{N_{s}}{N_{p}}$

Describe a transformer on the basis of the following points : Working method and principle

Important Questions on Alternating Current

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