Page 105 - Physics - XII

Q9. A diode’s reverse current is of the order of
(a) kA (b) mA (c) µA (d) A

Q10. What will happen when a p-n diode is reversed-biased?
(a) No current fl ows. (b) The depletion region is increased.

(c) The depletion region is reduced. (d) The height of the potential barrier is reduced.

Answer key

1. (c), 2. (b), 3. (a), 4. (a), 5. (b), 6. (a), 7. (b), 8. (c), 9. (c), 10. (b)

Case Study-based Questions

Read the paragraph and answer the questions that follow.
The process of applying the external voltage to a p-n junction semiconductor diode is called biasing.
When the positive terminal of the source is connected to the p-side and the negative terminal is connected

to n-side, then the junction diode is said to be connected in forward bias condition. When this external
voltage exceeds the threshold voltage, the current starts increasing exponentially. The value of threshold
voltage for silicon diode is 0.7 V and for germanium diode is 0.3 V.

When the positive terminal of the source is connected to the n-side and the negative terminal is connected
to p-side, then the junction diode is said to be connected in reverse bias condition. In reverse bias
conditions, a very small reverse current fl ows through the diode which is called reverse saturation current.

Q1. In which of the following fi gures, the p-n diode is forward biased?
(a) + 2 V (b)
+ 10 V

(c) + 7 V (d) + 7 V

+ 5 V + 2 V

Q2. If forward bias, the width of the potential barrier in a p-n junction diode
(a) increases. (b) decreases.
(c) remains constant. (d) fi rst increases, then decreases.

Q3. In a circuit as shown in the fi gure, if the diode forward voltage drop is 0.3 V, the voltage
diff erence between A and B is A
0.2 mA
(a) 1.3 V 5 kΩ

(b) 2.3 V

(c) 0 5 kΩ
(d) 0.5 V
B

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