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Question: Answered & Verified by Expert
Two point charges +Q and -Q having masses M and 2M respectively, are projected from the same point with the same velocity v in the region of a uniform magnetic field B such that the velocity makes an angle θ  with the magnetic field. If we neglect the mutual interaction between the particles, the distance from the point of projection where they will meet again for the first time is
PhysicsMagnetic Effects of CurrentJEE Main
Options:
  • A 2πMvcosθQB
  • B 8πMvcosθQB
  • C πMvcosθQB
  • D 4πMvcosθQB
Solution:
1306 Upvotes Verified Answer
The correct answer is: 4πMvcosθQB
Here path will be helical

T1=2πMQB

T2=2π2MQB

T2=4πMQB

They will meet again when the first particle completes two revolutions and the second particle completes one revolution so distance will be given as

d=vcosθt=vcosθ.22πMQB=4πMvcosθQB

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