(i) Name the type of a diode whose characteristics are shown in figure (a) and (b)
(ii) What does the point P in fig. (a) represent ?
(iii) What does the point P and Q in fig. (b) represent ?

Explanation

The characteristic curve (a) is of Zener diode and curve (b) is of solar cell.
(ii) The point p in fig. (a) represents Zener break down voltage.
(iii) In fig. (b), the point Q represents zero voltage and negative current, it means light falling on solar cell with ateast minimum threshold frequency gives the current in opposite direction to the due to a battery connected to solar cell. But for the point Q, the batter is short circuited. Hence represents the short circuit current.
In fig. (b), the point P represents some positive voltage on solar cell with zero current through solar cell.
It means, there is a battery connected to a solar cell which gives rise to the equal an opposite current to that in solar cell by virtue of light falling on it.
As current is zero for point P, hence we say P respresents open circuit voltage.