10th class Physics, Chapter 19: Electronics MCQs

1. A diode allows current to flow in:

1. (A) both directions
2. (B) neither direction
3. (C) one direction only ✓
4. (D) random directions

2. What is the primary function of a light-emitting diode?

1. (A) To block current in both directions
2. (B) To emit light when current passes in one direction ✓
3. (C) To amplify electrical signals
4. (D) To convert light into electrical energy

3. The output of a two inputs NOR gate is '1', when:

1. (A) A is '1' and B is '0'
2. (B) A is '0' and B is '1'
3. (C) both A and B are '0' ✓
4. (D) both A and B are '1'

4. The output of a NAND gate is '0', when:

1. (A) both of its inputs are '0'
2. (B) both of its inputs are '1' ✓
3. (C) any of its inputs is '0'
4. (D) any of its inputs is '1'

5. How many bits make up a byte in Boolean logic?

1. (A) 2
2. (B) 4
3. (C) 6
4. (D) 8 ✓

6. The most common semiconductors are:

1. (A) carbon and glass
2. (B) silicon and germanium ✓
3. (C) copper and silver
4. (D) iron and nickel

7. Adding a small amount of impurity to a semiconductor to increase its conductivity is called:

1. (A) rectification
2. (B) amplification
3. (C) ionization
4. (D) doping ✓

8. The majority charge carriers in an N-type semiconductor are:

1. (A) free electrons ✓
2. (B) holes
3. (C) protons
4. (D) neutrons

9. The majority charge carriers in a P-type semiconductor are:

1. (A) holes ✓
2. (B) free electrons
3. (C) neutrons
4. (D) photons

10. Which of the following is a pentavalent impurity used to make an N-type semiconductor?

1. (A) Gallium
2. (B) Silicon
3. (C) Phosphorus ✓
4. (D) Boron

11. Which of the following is a trivalent impurity used to make a P-type semiconductor?

1. (A) Arsenic
2. (B) Germanium
3. (C) Boron ✓
4. (D) Phosphorus

12. The region without free charge carriers at a PN junction is called the:

1. (A) base
2. (B) collector
3. (C) depletion region ✓
4. (D) conduction band

13. The voltage needed to overcome the barrier of a silicon diode is about:

1. (A) 3 V
2. (B) 12 V
3. (C) 0.7 V ✓
4. (D) 0.3 V

14. The voltage needed to overcome the barrier of a germanium diode is about:

1. (A) 1.5 V
2. (B) 5 V
3. (C) 0.3 V ✓
4. (D) 0.7 V

15. A diode is forward biased when its:

1. (A) both sides are connected to the negative terminal
2. (B) P-side is connected to the positive terminal of the battery ✓
3. (C) N-side is connected to the positive terminal
4. (D) both sides are connected to the positive terminal

16. In reverse bias the depletion region of a diode:

1. (A) remains unchanged
2. (B) widens ✓
3. (C) narrows
4. (D) disappears

17. Which of the following is NOT a use of a diode?

1. (A) Rectifier
2. (B) Voltage regulator
3. (C) Electronic switch
4. (D) Producing a magnetic field ✓

18. In an LED circuit a resistor is connected in series to:

1. (A) produce heat
2. (B) limit the current ✓
3. (C) increase the voltage
4. (D) convert A.C to D.C

19. The colour of the light emitted by an LED depends on the:

1. (A) material used in its manufacture ✓
2. (B) size of the bulb only
3. (C) colour of the wire
4. (D) current only

20. When electrons recombine with holes in an LED, the energy is released as:

1. (A) light ✓
2. (B) sound
3. (C) only heat
4. (D) magnetic field