Electro Magnetic Induction And Alternating Currents Question 210
Question: A transformer is used to light a 140 W, 24 V bulb from a 240 V a.c. mains. The current in the main cable is 0.7 A. The efficiency of the transformer is
Options:
A) $ 63.8% $
B) $ 83.3% $
C) $ 16.7% $
D) $ 36.2% $
Show Answer
Answer:
Correct Answer: B
Solution:
- Power of source $ =El=240\times 0.7=166 $
Efficiency
$ \Rightarrow Efficiency=\frac{140}{166}\Rightarrow \eta =83.3% $
