Verified Solution • 2025–26 Session moderate

QJEEM20Ph8f35: JEE Main 2020 Physics - Class 12 JEEM20Ph8f35 Solution: The figure shows a region of length ‘l’ with a uniform magnetic …

The figure shows a region of length ‘l’ with a uniform magnetic field of 0.3 T in it and a proton entering the region with velocity 4 ×\times 105 ms–1 making an angle 60o with the field. If the proton completes 10 revolution by the time it cross the region shown, ‘l’ is close to
(mass of proton = 1.67 ×\times 10–27 kg, charge of the proton = 1.6 ×\times 10–19 C) JEE Main 2020 (Online) 2nd September Evening Slot Physics - Magnetic Effect of Current Question 135 English

Multiple Choice Options

  • A 0.22 m
  • B 0.11 m
  • C 0.88 m
  • D 0.44 m

Step-by-Step Verified Solution

ll = 10 × pitch

= 10 ×\times vcos60o ×\times 2πmqB{{2\pi m} \over {qB}}

= 10 ×\times v ×\times 12{1 \over 2} ×\times 2πmqB{{2\pi m} \over {qB}}

= 10×4×105×3.14×1.67×10−271.6×10−19×0.3{{10 \times 4 \times {{10}^5} \times 3.14 \times 1.67 \times {{10}^{ - 27}}} \over {1.6 \times {{10}^{ - 19}} \times 0.3}}

= 0.44 m

Related Learning Resources & Exam Preparation

JEE Main PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring