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Quiz Chapter 6: Electricity and Magnetism

10 questions · Form 3 Science Bab 6: Electricity and Magnetism

Question 1 of 10Score: 0

If a household consumes 100 units of electricity in a month and the tariff is RM 0.20 per unit, what is the cost of electricity consumed?

Full Question List & Answer Key

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

1. If a household consumes 100 units of electricity in a month and the tariff is RM 0.20 per unit, what is the cost of electricity consumed?

  1. RM 2.00
  2. RM 20.00
  3. RM 200.00
  4. RM 50.00
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Answer: B

Cost = Energy (units) $×$ Rate = $100 × RM 0.20 = RM 20.00$.

2. What is the power rating of an electrical appliance that draws a current of $5 A$ when connected to a $240 V$ household supply?

  1. 48 W
  2. 245 W
  3. 1200 W
  4. 2400 W
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Answer: C

Power $P = V × I = 240 V × 5 A = 1200 W$ (or $1.2 kW$).

3. Where is a step-UP transformer placed within the National Grid Network?

  1. Between step-down sub-stations and residential homes
  2. Inside domestic consumer units
  3. Immediately after the power station generator
  4. Between high-voltage transmission lines and light industry
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Answer: C

Step-up transformers are located right at power stations to raise generated voltage (e.g. 11 kV or 25 kV) up to 132-500 kV before grid transmission.

4. What visual waveform appears on the screen of a Cathode Ray Oscilloscope (C.R.O.) when connected to a direct current (d.c.) voltage source with the time-base turned ON?

  1. Sinusoidal wave
  2. Square wave
  3. Straight horizontal line
  4. Vertical line
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Answer: C

Direct current flows in one direction with constant magnitude, producing a single horizontal line offset from the center on a C.R.O.

5. A step-up transformer has 200 turns in its primary coil and 1000 turns in its secondary coil. If an input voltage of 12 V a.c. is applied, what is the output voltage?

  1. 2.4 V
  2. 60 V
  3. 120 V
  4. 240 V
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Answer: B

Using $V_pV_s = N_pN_s arrow 12V_s = 2001000 = 15 arrow V_s = 12 × 5 = 60 V$.

6. What is the function of the earth wire (green/yellow striped) in a 3-pin plug?

  1. To carry current from the mains supply to the appliance
  2. To complete the circuit by returning current to the sub-station
  3. To safely direct leaked electric current from a metal body to the ground
  4. To step down voltage before it reaches internal circuits
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Answer: C

The earth wire connects the metallic outer chassis of an appliance to the ground, providing a low-resistance path that safely discharges leaked current.

7. Which light bulb technology exhibits the highest energy efficiency by converting most input electrical energy into light rather than heat?

  1. Incandescent filament bulb
  2. Compact Fluorescent Lamp (CFL)
  3. Light Emitting Diode (LED) bulb
  4. Halogen lamp
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Answer: C

LED bulbs lose very little energy as heat, converting up to 80-90% of electrical energy directly into visible light.

8. What color code is used for the LIVE wire in modern Malaysian standard fixed electrical wiring?

  1. Blue
  2. Green and yellow stripes
  3. Brown
  4. Black
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Answer: C

Under standard electrical color coding, Brown is Live, Blue is Neutral, and Green/Yellow stripes indicate Earth.

9. Why why electricity transmitted at extremely high voltages (e.g., 132 kV to 500 kV) through the National Grid Network?

  1. To increase current speed along cables
  2. To reduce current and minimize power lost as heat ($P = I2 R$)
  3. To eliminate the need for step-down sub-stations
  4. To prevent electrical theft along high-voltage pylons
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Answer: B

Stepping up voltage reduces transmission current ($I$). Since power loss as heat in cables depends on $I2 R$, lower current dramatically reduces energy loss.

10. Why are iron cores in transformers laminated into thin insulated sheets rather than solid blocks?

  1. To increase resistance of primary coils
  2. To reduce energy loss caused by induced eddy currents
  3. To prevent rusting of iron
  4. To enable direct current conversion
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Answer: B

Laminating the soft iron core breaks up circulating eddy currents within the core material, significantly reducing heat energy loss.

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