question_answer

Direction: Q.41 to Q.45

A transformer is an electrical device which is used for changing the AC voltages. It is based on the phenomenon of mutual induction i.e., whenever the amount of magnetic flux linked with a coil changes, an e.m.f. is induced in the neighbouring coil. For an ideal transformer, the resistances of the primary and secondary windings are negligible.

It can be shown that \[\frac{{{E}_{S}}}{{{E}_{P}}}=\frac{{{I}_{P}}}{{{I}_{S}}}=\frac{{{n}_{S}}}{{{n}_{P}}}=k\]

where the symbols have their standard meanings.

For a step up transformer,

\[{{n}_{S}}>{{n}_{P}};{{E}_{S}}>{{E}_{P}};k>1;\]

\[\therefore {{I}_{S}}<{{I}_{P}}\]

For a step down transformer,

\[{{n}_{S}}<{{n}_{P}};{{E}_{S}}<{{E}_{P}};k<1\]

The above relations are on the assumptions that efficiency of transformer is 100%.

Infact, efficiency \[\eta =\frac{\text{output}\,\,\text{power}}{\text{input}\,\,\text{power}}=\frac{{{E}_{S}}{{I}_{S}}}{{{E}_{P}}{{I}_{P}}}\]

Based on the above information, answer the following questions.

Which of the following quantity remains constant in an ideal transformer?

A) Current                         

B) Voltage

C) Power                           

D) All of these