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A transformer is an electrical device which is used for changing the a.c. voltage. It is based on the phenomenon of mutual induction. It can be shown that `(E_(s))/(E_(P)) = (I_(P))/(I_(s)) = (n_(s))/(n_(P)) = K` Where the symbols have their standard meaning. For a step up trasnformer,`K gt 1` and for a step down transformer, `K lt 1`. The above relations are on the assumption that efficiency to transformer is `100%` . In fact, efficiency `eta = ("outpu power")/("input power") = (E_(s) I_(s))/(E_(P) I_(P))` The number of turns in the primary and secondary coils of a transformer are 2000 and 50 respectively. The primary coil is connected to main supply of `120 V` and secondary to a night bulb `0.6 ohm`. The efficiency of transfomer is `80%` Current in night bulb isA. `5 A`B. `3 A`C. `0.5 A`D. `0.6 A` |
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Answer» Correct Answer - A Current in night bulb is `I_(s) = (E_(s))/(R_(s)) = (3)/(0.6) = 5 A` |
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