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Question: Answered & Verified by Expert
The magnetic flux through a loop of resistance $10 \Omega$ is given by $\phi=5 t^2-4 t+1$ Weber. How much current is induced in the loop after $0.2 \mathrm{sec}$ ?
PhysicsElectromagnetic InductionWBJEEWBJEE 2010
Options:
  • A $0.4 \mathrm{~A}$
  • B $0.2 \mathrm{~A}$
  • C $0.04 \mathrm{~A}$
  • D $0.02 \mathrm{~A}$
Solution:
2029 Upvotes Verified Answer
The correct answer is: $0.2 \mathrm{~A}$
Hints : $\phi=5 t^2-4 t+1$
$$
\frac{d \phi}{d t}=10 t-4
$$
$$
\mathrm{I}=\frac{e}{\mathrm{R}}=\frac{-d \phi / d t}{\mathrm{R}}=-\frac{10 t-4}{10}
$$
At $t=0.2 \mathrm{sec}$
$$
\mathrm{I}=\frac{-(10 \times 0.2-4)}{10}=-\frac{(2-4)}{10}=+\frac{2}{10}=+0.2 \mathrm{~A}=0.2 \mathrm{~A}
$$

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