Q: An electron and a proton are moving under the influence of mutual forces. In calculating the change in the kinetic energy of the system during motion, one ignores the magnetic force of one on another. This is, because
(a) The two magnetic force are equal and opposite, so they produce no net effect
(b) The magnetic forces do not work on each particle
(c) The magnetic forces do equal and opposite (but non-zero) work on each particle
(d) The magnetic forces are necessarily negligible
Ans: (b)