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JEE Main 202227 JulyEvening Shift
Exam
JEE Main
Year
2022
Date
27 July
Shift
Evening Shift
Subject
Physics
Chapter
Magnetic Effects of Current

JEE Main 2022 · 27 July · Evening Shift · Physics · Magnetic Effects of Current

A cyclotron is used to accelerate protons. If the operating...

A cyclotron is used to accelerate protons. If the operating magnetic field is 1.0T1 . 0T and the radius of the cyclotron 'dees' is 60cm60cm, the kinetic energy of the accelerated protons in MeVMeV will be :
[use mp=1.6×10−27kg,e=1.6×10−19C{m}_{p} = 1 . 6 \times {10}^{- 27}kg, e = 1 . 6 \times {10}^{- 19}C]

Options

  1. A1212
  2. B1818
  3. C1616
  4. D3232

Correct answer

B. 1818

Step-by-step solution

When the proton is rotated in a cyclotron its maximum velocity will be corresponding to the maximum radius of the circular path. We know that the radius of the circle in a magnetic field is given by,

r=mvBq⇒v=Bqrmr = \dfrac{mv}{Bq} ⇒ v = \dfrac{Bqr}{m}.

The kinetic energy will be,

K=12mv2=B2q2r22m⇒K=12×(1.6×10−19)2×(0.6)22×1.6×10−27×1.6×10−13MeV⇒K=18MeVK = \dfrac{1}{2}m{v}^{2} = \dfrac{{B}^{2}{q}^{2}{r}^{2}}{2m} ⇒ K = \dfrac{{1}^{2} \times {\left(1 . 6 \times {10}^{- 19}\right)}^{2} \times {\left(0 . 6\right)}^{2}}{2 \times 1 . 6 \times {10}^{- 27} \times 1 . 6 \times {10}^{- 13}}MeV ⇒ K = 18MeV

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