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State the principle which a transformer works. Describe the woeking of a transformer with necessary theory. |
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Answer» Solution :Transformer is a device to convert a low alternating current of high voltageinto high alternating current of low voltage and VICE versa. Principle : It works on the principle of mutual induction between two coils. Working : When an alternating emf is applied across the PRIMARY COIL, the input voltage changes with time. HENCE the magnetic flux through the primary also changes with time. This changing magnetic flux will be linked with secondary through the core. An emf is induced in the secondary.  Theory : Let `N_(1)` and `N_(2)` be the NUMBER of turns in the primary and secondary. Let `V_(P)` and `V_(S)` be the emf's across the primary and secondary. `(V_(S))/(V_(P))=("Out put emf")/("In put emf")=(-N_(2)(d phi)/(dt))/(-N_(1)(d phi)/(dt))=(N_(2))/(N_(1))` `therefore (V_(S))/(V_(P))=(N_(2))/(N_(1))` = Transformer ratio. Efficiency of transformer : It is the ratio of output power to the input power. `eta = ("Output power")/("Input power")xx100` |
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