Question
Mon November 28, 2011 By:

When current flows through the coil of the transformer, the core of the transformer gets hot. Why?

Expert Reply
Tue November 29, 2011
Transformers consist of two windings, primary and the secondary. When the voltage is connected to the primary coil , the AC current flows flows through and this current creates a magnetic field which passes to the secondary winding via the core of the transformer.
 

Transfer of electrical energy from the primary to the secondary is done via a magnetic field (called "flux") and a magnetic circuit called the "core of the transformer." To prevent losses, it is necessary to make sure the whole magnetic field created by the primary passes to the secondary. This is achieved by using an iron core, which has much lower magnetic resistance than air.

Losses are inevitable. They are present due to the fact that the windings exhibit a certain resistance value, which makes the transformer warm up during operation and this makes the core of the transformer hot.
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