JEE PYQ: Electromagnetic Waves Question 22
Question 22 - 2020 (07 Jan 2020 Shift 2)
A particle of mass $m$ and charge $q$ has an initial velocity $\vec{v} = v_0 \hat{j}$. If an electric field $\vec{E} = E_0 \hat{i}$ and magnetic field $\vec{B} = B_0 \hat{i}$ act on the particle, its speed will double after a time:
(1) $\frac{2mv_0}{qE_0}$
(2) $\frac{3mv_0}{qE_0}$
(3) $\frac{\sqrt{3}mv_0}{qE_0}$
(4) $\frac{\sqrt{2}mv_0}{qE_0}$
Show Answer
Answer: (3)
Solution
In x direction: $a_x = \frac{qE_0}{m}$. For speed to double: $v_0^2 + v_x^2 = (2v_0)^2$, $v_x = \sqrt{3}v_0 = a_x t$. $t = \frac{\sqrt{3}v_0 m}{qE_0}$.
BETA
