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Quiz Chapter 5: Electronics

10 questions ยท Form 5 Physics Bab 5: Electronics

Question 1 of 10Score: 0

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

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 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. Which formula correctly relates the Emitter current (I_E), Base current (I_B), and Collector current (I_C) of a functioning transistor?

  1. I_B = I_E + I_C
  2. I_E = I_B + I_C
  3. I_C = I_E + I_B
  4. I_E = I_C - I_B
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Answer: B

Total current entering/leaving the transistor requires I_E = I_B + I_C.

7. 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.

8. 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.

9. What is the function of the grid (control grid) inside a Cathode Ray Oscilloscope (CRO)?

  1. To focus the electron beam onto the screen
  2. To control the brightness of the light spot on the screen
  3. To deflect the electron beam horizontally
  4. To accelerate electrons to high speed
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Answer: B

The control grid is kept at negative potential relative to cathode; adjusting its voltage controls electron flow rate and spot brightness.

10. What property of a thermistor makes it ideal for fire alarm switching circuits?

  1. Its resistance decreases rapidly when temperature increases
  2. Its resistance increases when temperature increases
  3. It rectifies alternating current into direct current
  4. It emits light when heated
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Answer: A

A Negative Temperature Coefficient (NTC) thermistor experiences a steep drop in resistance as temperature rises.

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