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Quiz Chapter 5: Electronics

10 questions · Form 5 Physics Bab 5: Electronics

10 questions · plays in fullscreen

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. What happens to the depletion layer of a p-n junction diode when connected in FORWARD BIAS?

  1. It widens and increases resistance
  2. It narrows and resistance becomes very low
  3. It disappears permanently
  4. It remains unchanged
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Answer: B

Forward bias repels charge carriers across the junction, narrowing the depletion layer and allowing current to flow.

2. What impurity element is added to pure silicon to produce an n-type semiconductor?

  1. Boron
  2. Phosphorus
  3. Indium
  4. Gallium
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Answer: B

Pentavalent impurities such as Phosphorus or Arsenic provide extra free electrons, creating an n-type semiconductor.

3. Thermionic emission is defined as the process of releasing free electrons from the surface of a metal when it is:

  1. Exposed to ultra-violet radiation
  2. Heated to a high temperature
  3. Subjected to high pressure
  4. Placed inside a magnetic field
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Answer: B

Thermionic emission occurs when thermal energy supplies sufficient kinetic energy for free electrons to escape the heated metal surface.

4. Which operational feature characterizes a bridge rectifier during full-wave rectification?

  1. Current passes through 2 diodes during each half-cycle
  2. Current passes through all 4 diodes simultaneously
  3. Current flows through the load resistor in opposite directions each cycle
  4. Half of the input a.c. wave energy is discarded
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Answer: A

In a bridge rectifier, two specific diodes conduct during positive half-cycle and the other two conduct during negative half-cycle.

5. A potential divider circuit consists of a fixed 10 kΩ resistor and an LDR connected in series with a 6 V power source. In dark conditions, the resistance of the LDR is 20 kΩ. Calculate the potential difference across the LDR.

  1. 2 V
  2. 4 V
  3. 6 V
  4. 3 V
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Answer: B

V_LDR = [R_LDR / (R_fixed + R_LDR)] × V_total = [20 / (10 + 20)] × 6 V = (23) × 6 = 4 V.

6. How many diodes are required to construct a full-wave bridge rectifier circuit?

  1. 1
  2. 2
  3. 4
  4. 6
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Answer: C

A full-wave bridge rectifier requires 4 diodes arranged in a bridge configuration.

7. What is the effect of turning ON the Time-Base feature of a Cathode Ray Oscilloscope (CRO)?

  1. It sweeps the electron spot horizontally across the screen at a steady speed
  2. It deflects the spot vertically up and down
  3. It turns off the filament heater
  4. It converts a.c. input signals directly to d.c.
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Answer: A

The time-base applies a sawtooth voltage to horizontal X-deflection plates, sweeping the beam horizontally.

8. Electrons in a Cathode Ray Tube (CRT) are accelerated towards the anode by a potential difference of 2.5 kV. What is the kinetic energy acquired by each electron? (e = 1.6 × 10⁻¹⁹ C)

  1. 4.0 × 10⁻¹⁶ J
  2. 1.6 × 10⁻²² J
  3. 6.4 × 10⁻¹⁶ J
  4. 4.0 × 10⁻¹⁹ J
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Answer: A

Ek = e × V = 1.6 × 10⁻¹⁹ C × 2500 V = 4.0 × 10⁻¹⁶ J.

9. What are the majority charge carriers in a p-type semiconductor?

  1. Free electrons
  2. Holes
  3. Positive ions
  4. Negative ions
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Answer: B

In p-type semiconductors (doped with trivalent elements), holes act as majority charge carriers.

10. When a p-n junction diode is connected in REVERSE BIAS, current does not flow because:

  1. Electrons and holes are pushed towards the junction
  2. The depletion layer becomes wider and potential barrier increases
  3. The semiconductor material melts
  4. The diode acts as an ideal current amplifier
Show answer

Answer: B

Reverse bias pulls majority charge carriers away from the junction, widening the depletion layer and blocking conduction.

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