Electro Magnetic Induction And Alternating Currents Question 488
Question: In an inductor of self-inductance L=2mH, current changes with time according to relation $ i=t^{2}{{e}^{-t}} $ . At what time emf is zero?
Options:
A) 4s
B) 3s
C) 2s
D) Is
Show Answer
Answer:
Correct Answer: C
Solution:
-
$ L=2mH $ ,
$ i=t^{2}{{e}^{-t}} $
$ E=-L\frac{di}{dt}=-L[-t^{2}{{e}^{-t}}+2t{{e}^{-t}}] $
when $ E=0,-{{e}^{-t}}t^{2}+2t{{e}^{-t}}=0 $
or, $2t,{{e}^{-t}}={{e}^{-t}},t^{2}\Rightarrow t=2,\sec $ .
