Question
(i) Draw a labelled diagram of a step-down transformer. State the principle of its working.
(ii) Express the turn ratio in terms of voltages.
(iii) Find the ratio of primary and secondary currents in terms of turn ratio in an ideal transformer.
(iv) How much current is drawn by the primary of a transformer connected to 220 V supply when it delivers power to a 110 V- 550 W refrigerator?
Solution
i) Labelled diagram of a step-down transformer: soft iron core
Principle:
Transformer is based on the principle of electromagnetic mutual induction.
When the current flowing through the primary coil changes, an emf is induced in the secondary coil due to the change in magnetic flux linked with the primary coil.
Principle:
Transformer is based on the principle of electromagnetic mutual induction.
When the current flowing through the primary coil changes, an emf is induced in the secondary coil due to the change in magnetic flux linked with the primary coil.
ii) Turn ratio in terms of voltage is,
n =
iii) For an ideal transformer, according to the law of conservation of energy,
Input electrical power = Output electrical power.
IP VP = IS VS
i.e.,
iv) Given:
VS = 110 V ; Power,P = 550 W
Power, P = VP IP
n =
iii) For an ideal transformer, according to the law of conservation of energy,
Input electrical power = Output electrical power.
IP VP = IS VS
i.e.,
iv) Given:
VS = 110 V ; Power,P = 550 W
Power, P = VP IP
