JEE Main20202 Sep 2020Evening ShiftPhysicsMagnetic Effects of CurrentActual
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 × 10 5 m s - 1 making an angle 60 ° 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 × 10 - 27 kg , charge of the proton = 1 . 6 × 10 - 19 C )
Options
- A0 . 11   m
- B0 . 88   m
- C0 . 44   m
- D0 . 22   m
Correct answer
C. 0 . 44   m
Step-by-step solution
ℓ = 10 × pitch = 10 × v cos 60 ° × 2 π m gB ℓ = 10 π mv qB Put in the value of given data we find ℓ = 0 . 44   m