Question

Electric and Magnetic Forces: IN a laboratory experiment, there is a region containing both an electric and a magnetic field. the strength of the electric field is 3,000V/m/ The strength of the magnetic field is .5 T. The fields act on a moving electron to produce no net force. (a) What is the minimum speed v of the electron. (b) Draw the vectors E, B, and v

Answer 1

Given

electric field is E = 3000 V/m

magnetic fieldis B = 0.5 T

charge of electron is q = 1.6*10^-19 C

the force acting on the electron is both electric and magnetic foorce

F_e = E*q

F_m = q*V*B sin theta

given the net force on electron is zero  

that is the two forces are directed in opposite directions to each other

E*q = q*V*B sin theta

for minimum speed of the electron the angle theta is 90 degrees

v = E/B sin90 = E/B

v = 3000 /(0.5) = 6000 m/s

the speed of the electron is 6000 m/s

let the electric field is along +x axis then the magnetic field is along -x axis

and the direction of velocity of the electron is perpendicular to the magnetic field