Problem 1 An electron is accelerated from rest in the plane of the page parallel

Question

Problem 1 An electron is accelerated from rest in the plane of the page parallel to the page's long edge (bottom to top) by a potential difference of 400 V. The electron then enters a uniform magnetic field of magnitude 0.2 T directed into the page with its velocity perpendicular to the field. (a) What are the magnitude and direction of an electric field that will cause the electron to continue to move without being deflected? Ignore gravity. The electric field is now removed. (b) Calculate the radius of the electron's path in the magnetic field

Explanation / Answer

given V = 400 V

electron accelerated from rest

hence final speed = u

0.5mu^2 = qV

u = 1.1859989*10^7 m/s

B = 0.2 T

a. the electric field to cancel the magnetic force is to the right

and

this is given by

qE = q*u*B

hence

E = uB = 2.371*10^6 V/m

b. radius of path = r

mv^2/r = qvB

r = mu/qB = 0.284 mm

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