1. Which of the following would not be used as an impurity in doping silicon?
(a) Germanium.
(b) Gallium.
(c) Boron.
(d) Phosphorus.
(e) Arsenic.
2. Why are metals good conductors?
(a) Gaining a tiny bit of energy allows their electrons to move.
(b) They have more electrons than protons, so some of the electrons are extra and free to move.
(c) They have more protons than electrons, so some of the protons are extra and free to move.
(d) Gaining a tiny bit of energy allows their protons to move.
(e) Electrons are tightly bound to their atoms.