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An electron moves with velocity v = (4.0i – 6.0ij) x 104 m/s in a magnetic field B= (-0.80i + 0.60j) T. Determine the magnitude and direction of the force on the electron.

F=ma: qvB=m*v^2/r : r= mv/qB

r = (9.1E^-31kg * (4.0i – 6.0ij) x 104 m/s) / (1.6E^-19 C * (-0.80i + 0.60j) T)

= (3.8E-28i + -5.7E-28j) / (-1.28E-19i + 9.6E-20j)T

= (-3E-9i - 5.9E-9j)T

qvB=m*v^2/r

= 9.1E^-31kg (3.8E-28i * -5.7E-28j)2 / (-3E-9i - 5.9E-9j)T

=(-4.44E-77i + 5.011E-77)T N southward.

I'm totally stuck on this problem. This is my work but I'm pretty sure it's wrong. I'm not sure how to handle the i, j, k component problems. or is this the way... take the i and j components of the velocity and the magnetic field, and find two separate force components, Fi and Fj. Then assume i and j are perpendicular vectors and then with Fi and Fj find the

magnitude of the force. Finally, find the angle in the i-j plane in this

way, knowing that the force would come into the k plane but not at a

right angle to both i and j?? is that correct?

thanks, any help would be appreciated.

Air K

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# Homework Help: Electrons and magnetism.

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