(i) Name the type of a diode whose characteristics are shown in Fig. 14.9 (A) and Fig. 14.9(B).
Fig.14.9(A) is the characteristic of any PN junction diode. The first quadrant represents the forward bias of the diode. P is the point where it reaches the break down voltage. Depending on the value of P we can further classify them to zener or normal PN junction diode.
Fig.14.9(B) is the characteristic of photo electric diode.
(ii) What does the point P in Fig. (A) represent?
P is called the knee or the breakdown voltage. At this point the current vigorously increases.
(iii) What does the points P and Q in Fig. (B) represent?
We can see that at point Q, V = 0. Current is maximum at this point. At point Q current completely vanishes. This voltage at this point is called the stopping potential.
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(a) A student wants to use two p-n junction diodes to convert alternating current into direct current. Draw the labelled circuit diagram she would use and explain how it works.
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Consider a box with three terminals on top of it as shown in Fig.14.18 (a):
Three components namely, two germanium diodes and one resistor are connected across these three terminals in some arrangement.
A student performs an experiment in which any two of these three terminals are connected in the circuit shown in Fig. 14.18 (b).
The student obtains graphs of current-voltage characteristics for unknown combination of components between the two terminals connected in the circuit.
The graphs are
(i) when A is positive and B is negative
(ii) when A is negative and B is positive
(iii) When B is negative and C is positive
(iv) When B is positive and C is negative
(v) When A is positive and C is negative
(vi) When A is negative and C is positive
From these graphs of current – voltage characteristic shown in Fig. 14.18 (c) to (h), determine the arrangement of components between A, B and C.
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