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KCET · Physics · Magnetic Effects of Current

A proton and an alpha-particle moving with the same velocity enter a uniform magnetic field with their velocities perpendicular to the magnetic field. The ratio of radii of their circular paths is

  1. A \(2: 1\)
  2. B \(1: 4\)
  3. C \(4: 1\)
  4. D \(1: 2\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(1: 2\)

Step-by-step Solution

Detailed explanation

Radius of charged particle moving on circular
path in uniform magnetic field,
\(r =\frac{m v}{B q} \)
\( r \propto \frac{m}{q} \)
\( \frac{r_p}{r_\alpha} =\frac{m_p}{m_\alpha} \cdot \frac{q_\alpha}{q_p}=\frac{m_p}{4 m_p} \times \frac{2 e}{e}=\frac{1}{2}\)
\(\Rightarrow r_p: r_\alpha=1: 2\)