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State the underlying principle of a transformer and obtain the expression for the ratio of secondary to primary voltage in terms of the three (i) number of secondary and primary winding send (ii)primary and secondary currents. |
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Answer» Solution :PRINCIPLE of a transformer : When the alternating current flows through the primary coil and EMF is induced in the neighbouring (secondary) coil (i) Let `(d phi)/(d t)` be the rate of change of FLUX through each TURN of the primary and the secondary coil `(epsilon_(1))/(epsilon_(2)) = -N_(1).(d phi)/(d t)//-N_(2).(d phi)/(d t) = (N_(1))/(N_(2))` or `(V_(1))/(V_(2)) = (N_(1))/(N_(2))` ...(i) (ii) But for an ideal transformer , `V_(1)I_(1) = V_(2)I_(2)` `(V_(1))/(V_(2)) = (I_(2))/(I_(1))` ...(ii) from equation (i) and (ii) `(V_(1))/(V_(2)) = (N_(1))/(N_(2)) = (I_(2))/(I_(1))` |
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