Electrons are emitted from a conductor when the conductor is A. subjected to a small voltage. B. bombarded by high-speed electrons. C. cooled rapidly. D. exposed to weak light.
B. Bombarded by high speed electrons. There are already electrons with potential energy in the conductor. When it is bombarded by these high speed electrons, the potential energy is changed into kinetic energy and then the electrons are emitted from the conductor. Hope this helps.