1. Which of the following statements about the force on a charged particle due to a magnetic field are not valid?
(a) It depends on the particle's charge.
(b) It depends on the particle's velocity.
(c) It depends on the strength of the external magnetic field.
(d) It acts at right angles to the direction of the particle's motion.
(e) None of the above; all of these statements are valid.
2. Two parallel wires are vertical. The one on the left carries a 10-A current upward. The other carries 5-A current downward. Compare the magnitude of the force that each wire exerts on the other.
(a) The wire on the left carries twice as much current, so it exerts twice the force on the right wire as the right one exerts on the left one.
(b) The wire on the left exerts a smaller force. It creates a magnetic field twice that due to the wire on the right; and therefore has less energy to cause a force on the wire on the right.
(c) The two wires exert the same force on each other.
(d) Not enough information; we need the length of the wire.