Which one of the following is true at the instant shown? (a) Current is flowing through R from a to b. (b) Current is flowing through R from b to a. (c) There is no current flowing through R. (d) The rod experiences no net force.

Which of the following best describes the magnitude of the current in R subsequent to the instant shown? (a) The magnitude increases because the rod speeds up. (b) The magnitude decreases because resistance always decreases current over time. (c) The magnitude decreases because the rod slows down. (d) The magnitude remains constant because the rod travels with constant speed.

 

Questions 3-4 refer to: The figure shows a conducting rod sliding over two bare wires. The wires are in a horizontal plane (ignore gravity) and are connected through the resis- tor R. A uniform magnetic field points out of the page everywhere. Friction between the rod and the wires is neg- ligible. At the instant shown, the rod is moving from right to left, toward R, with a speed v. (A hand got the rod started before the instant shown, but is no longer in contact with it.) R a b B, out B, out B, out B, out