JEE PYQ: Magnetic Effects Of Current Question 11
Question 11 - 2020 (02 Sep 2020 Shift 2)
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 $4 \times 10^5$ ms$^{-1}$ making an angle $60°$ with the field. If the proton completes $10$ revolutions by the time it crosses 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)
(1) $0.11$ m
(2) $0.88$ m
(3) $0.44$ m
(4) $0.22$ m
Show Answer
Answer: (3) $0.44$ m
Solution
$l = 10 \times v\cos 60° \times \frac{2\pi m}{qB} = \frac{20\pi mv}{2qB} \approx 0.44$ m.
BETA
