# Class 12 Physics MCQ – Semiconductor Diode

This set of Class 12 Physics Chapter 14 Multiple Choice Questions & Answers (MCQs) focuses on “Semiconductor Diode”.

1. Why is there a sudden increase in current in Zener diode?
a) Due to the rupture of ionic bonds
b) Due to rupture of covalent bonds
c) Due to viscosity
d) Due to potential difference

Explanation: The sudden increase in current in a Zener diode is due to the rupture of the many covalent bonds present. Therefore, the Zener diode should be connected in reverse bias.

2. What is the semiconductor diode used as?
a) Oscillator
b) Amplifier
c) Rectifier
d) Modulator

Explanation: Semiconductor diode can be used as a rectifier. The function of a rectifier is that it converts an alternating current into direct current by allowing the current to pass through in one direction.

3. What is an oscillator?
a) An amplifier with a large gain
b) An amplifier with negative feedback
c) An amplifier with positive feedback
d) An amplifier with no feedback

Explanation: An oscillator is considered as an amplifier with positive feedback. It converts direct current from a power supply to an alternating current signal. It produces an alternating waveform without any input.

4. What is rectification?
a) Process of conversion of ac into dc
b) Process of conversion of low ac into high ac
c) Process of conversion of dc into ac
d) Process of conversion of low dc into high dc

Explanation: Rectification is the process of conversion of alternating current into direct current. The conversion first powers to alternating current then use a transformer to change the voltage, and finally rectifies power back to direct current.

5. What is a Zener diode used as?
a) Oscillator
b) Regulator
c) Rectifier
d) Filter

Explanation: Zener diode can be used as a voltage regulator. They can also be used as shunt regulators to regulate the voltage across small circuits. Zener diodes are always operated in a reverse-biased condition.
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6. Forward biasing of p-n junction offers infinite resistance.
a) True
b) False

Explanation: No, this is a false statement. Forward biasing of p-n junction offers low resistance. In the case of an ideal p-n junction, the resistance offered is zero. So, forward biasing does not offer any resistance.

7. When a junction diode is reverse biased, what causes current across the junction?
a) Diffusion of charges
b) Nature of material
c) Drift of charges
d) Both drift and diffusion of charges

Explanation: The reverse current is mainly due to the drift of charges. It is due to the carriers like holes and free electrons passing through a square centimeter area that is perpendicular to the direction of flow.

8. Identify the condition for a transistor to act as an amplifier.
a) The emitter-base junction is forward biased and the base-collector junction is reverse biased
b) No bias voltage is required
c) Both junctions are forward biased
d) Both junctions are reverse biased

Explanation: In order to use a transistor as an amplifier the emitter-base junction is set up as forward biased and the base-collector junction is set up as reverse biased. This is the criteria for making a transistor function as an amplifier.

9. What can a p-n junction diode be used as?
a) Condenser
b) Regulator
c) Amplifier
d) Rectifier

Explanation: A junction diode can be used as a rectifier. The rectifier converts alternating current into direct current. During the positive half cycle, the diode is forward biased and allows electric current through it.

10. What is a transistor made up of?
a) Chip
b) Insulator
c) Semiconductor
d) Metal

Explanation: A transistor is a semiconductor device. Transistors can work either as an amplifier or as a switch. It is used to amplify or switch electronic signals. A transistor is a solid-state device made up of silicon and germanium.

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