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.