Construction and working of a transformer
It was previously shown that a change in the current in one of two neighboring coils cause an emf to be generated in the other coil. The induced emf and, therefore, the induced current can be greatly increased iron core. This combination of two coils and an iron core is one type of transformer. Suppose that an alternating current is maintained in the primary coil of the transformer. This current is constantly changing; hence the magnetic flux in the iron core also varies periodically, there by producing an alternating emf in the secondary coil.
Since the rate of change of flux is nearly the same in the primary and secondary coils, it follows that the induced emfs in the coils are directly proportional to the respective numbers of turns proportional to the respective numbers of turns in the coils. Symbolically
Where ε is used for induced emf and N for the number of turns. In proactive the voltage impressed on the primary from the outside source is somewhat greater than εp the induced emf in the primary, and the secondary voltage at the terminals is slightly less than εs, the emf induced emf in the primary is nearly equal to the power output from the secondary.
The currents are thus seen to be inversely proportional to the respective voltages (approximately)
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