Question

A current of 5 A is flowing at 220 V in the primary coil of a transformer. if the voltage produced in the secondary coil is 2200 V and 50% of power is lost, then the current in secondary will be
A) 2.5 A
B) 0.5 A
C) 0.25 A
D) 5 A

Answer 1

Hint:In addition to voltage and current, there is another important parameter related to electrical circuits is Power.
Power, In electric circuits is a function of both voltage and current.

Complete Step by step solution: Given Voltage at primary coil Vp=220V,
Voltage at secondary coil Vs=2200V,
Current in primary coil Ip=5A,
Current in secondary coil Is=?
Power loss = 50% Efficiency of transformer (n)

Power loss is defined as the ratio of power output to input power
$\eqalign{
  & {\text{i}}{\text{.e}}{\text{., 50 = }}\dfrac{{{\text{2200 }} \times {\text{ Is}}}}{{220{\text{ }} \times {\text{ 5}}}} \times 100 \cr
  & {\text{Is = 0}}{\text{.25 A}} \cr} $


Hence option C is correct

Additional Information: In electric circuits, power is a function of both voltage and current.
P =IE, In this case however, the power (P) is exactly equal to the current (I) multiplied by the voltage (E), instead of being simply proportional to IE. When using this formula, the unit of measure for power is the watt, abbreviated with the letter W.
It should be understood that neither voltage nor current constitute energy by themselves. Rather, power is the combination of voltage and current in a circuit. Remember that voltage is the specific work (or potential energy) per unit charge, while current is the speed at which electrical charges move through a conductor.

Voltage (specific work) is analogous to the work done by lifting a weight against the force of gravity. The current (rate) is analogous to the speed at which that weight is lifted. Together, as a product (multiplication), voltage (work) and current (rate) constitute power.

As with the diesel tractor engine and motorcycle engine, a high voltage low current circuit may be dissipating the same amount of power as a low voltage, high current circuit. Neither the amount of voltage alone nor the amount of current alone indicates the amount of energy in an electrical circuit.

Notes:In an open circuit, where there is voltage between the source terminals and there is zero current, there is no power dissipated, no matter how large that voltage is. Since P = IE and I = 0 and anything multiplied by zero is zero, the power dissipated in any open circuit must be zero.