The primary of a 3:1 step-up transformer is connected to a source and the secondary is connected to a resistor R.The power dissipated by R in this situation is P.If R is connected directly to the source it will dissipate a power of:
A)P/9
B)P/3
C)P
D)3P
E)9P

Question

Quizplus · Accepted Answer

In a 3:1 step-up transformer, the voltage across the secondary is three times the primary voltage. If R is connected directly to the source, the voltage across it will be one-third of what it was when connected to the secondary. Since power is proportional to the square of the voltage (P = V^2/R), the power dissipated will be (1/3)^2 = 1/9 of the original power P.

The Primary of a 3:1 Step-Up Transformer Is Connected to a Source