WAEC Physics 2015 Theory — Question 5

Model answer

(a) Doping is the deliberate introduction of impurity atoms into a pure (intrinsic) semiconductor material to alter and control its electrical conductivity, creating either an excess of free electrons (n-type) or of holes (p-type). (b) OR gate symbol: a shield/curved shape with two inputs A and B on the flat curved back and a single pointed output labelled A+B, representing the Boolean logic OR gate where the output is true if either or both inputs are true.