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Quiz Chapter 5: Electronics

10 questions · Form 5 Physics Bab 5: Electronics

Question 1 of 10Score: 0

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

Full Question List & Answer Key

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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. Which set of properties correctly describes cathode rays inside a vacuum tube?

  1. Electromagnetic waves, positively charged, deflected by electric field
  2. Stream of fast electrons, negatively charged, deflected towards positive plate
  3. Stream of protons, positively charged, undeflected by magnetic field
  4. Stream of neutrons, neutral charge, cause fluorescence
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Answer: B

Cathode rays consist of high-speed electrons (negative charge) that deflect toward positive electric plates.

3. What component is connected across the load resistor in a rectifier circuit to smooth out voltage ripples?

  1. Capacitor
  2. Inductor
  3. Zener diode
  4. Thermistor
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Answer: A

A capacitor acts as a smooth-filter by charging at peak voltage and discharging when rectified output voltage drops.

4. In a transistor current amplifier circuit, an increase in base current of 20 µA produces an increase in collector current of 2.0 mA. What is the current amplification factor (β)?

  1. 100
  2. 10
  3. 200
  4. 50
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Answer: A

Amplification factor β = ΔI_C / ΔI_B = 2.0 × 10⁻³ A20 × 10⁻⁶ A = 100.

5. Which sensor component is best suited for use in a transistor circuit designed to automatically turn ON streetlights at night?

  1. Thermistor
  2. Light Dependent Resistor (LDR)
  3. Diode
  4. Microphone
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Answer: B

An LDR changes its resistance based on ambient light level (high resistance in darkness), making it suitable for night-time switches.

6. 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.

7. 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.

8. An electron moving at 2.0 × 10⁷ m s⁻¹ enters an electric field in a CRT. Calculate its kinetic energy. (m = 9.1 × 10⁻³¹ kg)

  1. 1.82 × 10⁻16 J
  2. 3.64 × 10⁻16 J
  3. 1.82 × 10⁻23 J
  4. 9.10 × 10⁻17 J
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Answer: A

Ek = 0.5 × m × v² = 0.5 × (9.1 × 10⁻³¹ kg) × (2.0 × 10⁷ m s⁻¹)² = 1.82 × 10⁻¹⁶ J.

9. Doping a pure semiconductor crystal with trivalent impurity atoms (e.g., Boron) introduces:

  1. Extra free electrons into the conduction band
  2. Electron deficiencies known as holes
  3. High concentration of heavy positive ions
  4. Zero electrical conductivity
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Answer: B

Trivalent atoms have 3 valence electrons, leaving one unfilled covalent bond position (hole).

10. 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.

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