Question

A point charge is moving with speed 2 × 107 m/s parallel to the x axis along strait line at y=2 m. At t = 0, the charge is at x = 0 m. The magnitude of the magnetic field at x = 4 m is B0 at the origin. The magnitude of the magnetic field at at origin when t = 0.15 μs is?

Answer 1

Answer:

$B_2  = 4B_1$

Explanation:

initial distance of point from the electron is r_1 = 4 m

distance moved by electron is x

x = vt

$x = 2*10^{7} *0.1*10^{-6}$

x = 2 m

new distance of point from electron is r_2 = 2m

field due to moving charge is

$B = \frac{ \mu_o 4vr}{4 \pi r^3}$

CHARGE IS INVERSELY PROPOTIONAL TO DISTANCE FROM ELECTRON.

therefore$\frac{B_1}{B_2} = [\frac{r_2}{r_1}]^2$

                         $= [\frac{2}{4}]^2$

$B_2  = 4B_1$