Phy 132 - Assignment 7
A. 1. No force. F = q v x B, and both v and B point in the +x direction. The
cross product of parallel vectors is zero, because of the sinθ factor.
2.
B. 1. . A north magnetic pole means north seeking. Since opposites attract, this
means that the geographic north of the Earth contains a magnetic south pole.
2.
C. 1. a. No - Although it carries a current, the wire is still neutral: As quickly as
charge flows in
one end, it flows out the other, so the wire develops no net charge.
b. Yes - A current in a B field feels a force: F = I l xB.
2.
D. 1. a. Yes - A charge always feels a force in an E field.
b. Yes, because the charges are in motion.
2.
E. 1. a. Yes - A charge always feels a force in an E field.
b. No - Charges feel force in a B field only if they are moving.
2.
F. 1. a. The proton follows a circular path. (For the reasons explained in class.)
b. There are a couple of possible answers. One is that the electron would curve
in the opposite direction
due to its opposite charge. The
other is that its path would have a smaller radius due to its smaller mass.
2.