KCET · Physics · Magnetic Effects of Current
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
- A \( \frac{r}{2} \)
- B \( 2 r \)
- C \( \frac{r}{4} \)
- D \( 4 r \)
Answer & Solution
Correct Answer
(B) \( 2 r \)
Step-by-step Solution
Detailed explanation
The radius of the circular path followed by an electron in uniform magnetic field is given by
\(r=\frac{m v}{q B}\)
\(\Rightarrow r \propto \frac{1}{B}\)
\(r=\frac{m v}{q B}\)
\(\Rightarrow r \propto \frac{1}{B}\)
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