Electro Magnetic Induction And Alternating Currents Question 415
Question: The self-inductance of a choke coil is 10 mH. When it is connected with a 10 V dc source, then the loss of power is 20 watt. When it is connected with 10 volt ac source loss of power is 10 watt. The frequency of ac source will be
Options:
A) 50 Hz
B) 60 Hz
C) 80 Hz
D) 100 Hz
Show Answer
Answer:
Correct Answer: C
Solution:
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With dc: $ P=\frac{V^{2}}{R}\Rightarrow R=\frac{{{(10)}^{2}}}{20}=5\Omega ; $
With ac: $ P=\frac{V_{rms}^{2}R}{Z^{2}}\Rightarrow Z^{2}=\frac{{{(10)}^{2}}\times 5}{10}=50,{{\Omega }^{2}} $
Also $ Z^{2}=R^{2}+4{{\pi }^{2}}V^{2}L^{2} $
$ \Rightarrow 50={{(5)}^{2}}+4{{(3.14)}^{2}}V^{2}{{(10\times {{10}^{-3}})}^{2}}\Rightarrow v=80Hz $
