posted by Busker on .
Suppose there are two transformers between your house and the high-voltage transmission line that distributes the power. In addition, assume your house is the only one using electric power. At a substation the primary of a step-down transformer (turns ratio = 1:25) receives the voltage from the high-voltage transmission line. Because of your usage, a current of 67.5 mA exists in the primary of the transformer. The secondary is connected to the primary of another step-down transformer (turns ratio = 1:39) somewhere near your house, perhaps up on a telephone pole. The secondary of this transformer delivers a 240-V emf to your house. How much power is your house using? Remember that the current and voltage given in this problem are rms values.
Io2 = 67.5mA * 25 * 39 = 65,812.5 mA = 65.81 A.= Output current of T2.
Po2=Vo2 * Io2=240 * 65.81=15,795 Watts =
Power output of T2 = Power used by home.