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MHT CET · Physics · Magnetic Effects of Current

An alternating electric field of frequency ' \(v^{\prime}\) is applied across the dees of a cyclotron which is used to accelerate protons of mass 'm'. The radius of the dees is 'R'. The operating magnetic field used in cyclotron is 'B'. The kinetic energy of the proton beam is given by

  1. A \(2 m \pi^{2} v^{2} R^{2}\)
  2. B \(2 m \pi v^{2} R^{2}\)
  3. C \(m \pi^{2} v^{2} R^{2}\)
  4. D \(m \pi v^{2} R^{2}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(2 m \pi^{2} v^{2} R^{2}\)

Step-by-step Solution

Detailed explanation

Time period of cyclotron is
\(\mathrm{T}=\frac{1}{\mathrm{v}}=\frac{2 \pi \mathrm{m}}{\mathrm{eB}} ; \mathrm{B}=\frac{2 \pi \mathrm{m}}{\mathrm{e}} \mathrm{v} ; \mathrm{R}=\frac{\mathrm{mv}}{\mathrm{eB}}=\frac{\mathrm{P}}{\mathrm{eB}}\)
\(\Rightarrow \mathrm{P}=\mathrm{eBR}=\mathrm{e} \times \frac{2 \pi \mathrm{mv}}{\mathrm{e}} \mathrm{R}=2 \pi \mathrm{mvR}\)
\(\mathrm{K.E.}\) \(=\frac{\mathrm{P}^{2}}{2 \mathrm{m}}=\frac{(2 \pi \mathrm{mvR})^{2}}{2 \mathrm{m}}=2 \pi^{2} \mathrm{mv}^{2} \mathrm{R}^{2}\)