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A hypothetical ideal transformer considered as...
A hypothetical ideal transformer considered as a circuit element, consisting of N P turns in the primary winding, and N S in the secondary. Electrical power supplied to the primary circuit is delivered to the load in secondary circuit by means of mutual induction. The time-varying magnetic flux in the core generates an electromagnetic force over each of the windings. The voltage and current relationships are shown below. (Photo credit: Wikipedia)

Please explain what is transformer and tell what is the reason behind the working of transformer that it reduces potenial when current is high and increases potential when current is low?

Explain widely and deeply with concepts.


Transformer is a device based on mutual inductance and is used to change the voltage of alternating (or varying) current. There are two types of transformers – stepup and stepdown.

A step-up transformer increases the voltage as the step-down transformer decreases the ac voltage.

When a transformer changes the alternating voltage, it is not adding any power, it only transforms the voltage.

As power is the product of voltage and current, as voltage increases, the current decreases. (and vice versa)

The following links will help you understand transformers in great detail.


Sir,im not understanding how transformer works?while current is going from one station to other we keep high voltage and very less current to decrease power loss but current is proportional to voltage how can u make low current using high voltage?

Asked  Avinah Boinepalle



A transformer works on the principle of mutual induction. [mutual induction is the phenomenon of production of emf in a coil due to the change in the strength of current through a neighbouring coil]

Transformers are of two kinds – step up and step down.

A step up transformer converts low voltage (high current) ac to high voltage (low current) ac.

In the case of an ideal transformer, there is no power loss.

In that case,

input power = out power

Vin Iin = Vout Iout

[This equation shows how an increase in output voltage results in a decrease in out put current]

Long distance transmission of ac requires low  current as the heat dissipated during transmission is proportional to the square of current.

If we use a step-up transformer , it steps up the voltage and consequently steps down the current so that VI is the same.

In the case of real transformers, there are some power losses within the transformner, however, an increase in output current through mutual induction will essentially result in a decrease in output current.

Hope that the matter is clear now. In case of doubt, please post them as comments to this post.

What energises the secondary of the Transformer?

Jamie asks:

“I am told that no magnetism escapes from a transformer due to the closed loop. If that is the case, what is energizing the secondary winding?”

Buzzing sound from a transformer – Magnetostriction

Subasaraswathi asks:

Why does a buzzing sound come from an electric transformer?

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