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Question: Answered & Verified by Expert
An electron is moving in a circle of radius \( r \) in a magnetic field B. Suddenly the field is reduced
to \( \frac{B}{2} \). The radius of the circular path is
PhysicsMagnetic Effects of CurrentKCETKCET 2018
Options:
  • A \( \frac{r}{2} \)
  • B \( 2 r \)
  • C \( \frac{r}{4} \)
  • D \( 4 r \)
Solution:
1442 Upvotes Verified Answer
The correct answer is: \( 2 r \)
The radius of the circular path followed by an electron in uniform magnetic field is given by
\[
\begin{array}{l}
r=\frac{m v}{q B} \\
\Rightarrow r \propto \frac{1}{B}
\end{array}
\]

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