In: Physics
an electron is moving with a speed of 2.9E5 m/s when it moves in the positive x direction, it feels no force. When it moves in the positive y direction it experiences a force of 3.3E-14N that points in the negative z direction. What is the magnitude and direction of the magnetic field?
F = q (v B) ; denotes the cross product.
CASE I There is no force in the x-direction.
So v B = 0
vBsin = 0
So the angle between v and B is 0 i.e = 0.
====> the direction of the magnetic field is either along +x or -x direction.
CASE II Force when moving in y-direction.
F = q (v B)
3.3E-14 = 1.6E-19( 2.9E5 * B sin )
(Here = 90o as the direction of velocity is in y and that of B is along x)
Solving the above equation; we get B = 0.711 T
Also the direction of the force is along -ve z direction, so using the right hand thumb rule it can clearly be stated that the direction of the magnetic field is along +x axis.
So; B = 0.711 T along +ve x-axis.