Page 106 - Physics - XII

Q4. If the voltage of the potential barrier is V , a voltage V is applied to the input. At what
0
moment will the barrier disappear?

(a) V < V (b) V = V (c) V > V (d) V << V 0
0
0
0
Answer key
1. (c), 2. (b), 3. (b), 4. (b)

Assertion-Reason Type Questions

These consist of two statements—Assertion (A) and Reason (R). Answer these questions by selecting
the appropriate option given below:
a. Both A and R are true and R is the correct explanation of A.
b. Both A and R are true and R is not the correct explanation of A.

c. A is true but R is false. d. A is false but R is true.
1. Assertion (A) : We can measure the potential barrier of p-n junction by putting a sensitive
voltmeter across its terminals.

Reason (R) : The current through the p-n junction is not same in forward and reverse bias.
2. Assertion (A) : The resistance of p-n junction is low when forward biased and is high when
reverse biased.

Reason (R) : In reversed biased, the depletion layer is reduced.
3. Assertion (A) : The resistivity of a semiconductor decreases with temperature.

Reason (R) : The atoms of a semiconductor vibrate with larger amplitude at higher temperatures,
thereby increasing its resistivity.

4. Assertion (A) : When two semiconductors of p and n-type are brought in contact, they form p-n
junction which acts like a rectifi er.
Reason (R) : A rectifi er is used to convert alternating current into direct current.

5. Assertion (A) : Silicon is preferred over germanium for making semiconductor devices.
Reason (R) : The energy gap in germanium is more than the energy gap in silicon.

Answer key

1. (d), 2. (c), 3. (c), 4. (b), 5. (c)

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