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Quiz Chapter 3: Electricity

10 questions · Form 5 Physics Bab 3: Electricity

Question 1 of 10Score: 0

Two resistors of 6 Ω and 12 Ω are connected in PARALLEL across a 12 V power supply. What is the total current supplied by the source?

Full Question List & Answer Key

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

1. Two resistors of 6 Ω and 12 Ω are connected in PARALLEL across a 12 V power supply. What is the total current supplied by the source?

  1. 3 A
  2. 1 A
  3. 2 A
  4. 0.67 A
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Answer: A

Effective resistance 1R = 16 + 112 = 312 => R = 4 Ω. Total current I = VR = 12 V4 Ω = 3 A.

2. A beam of electrons delivers 3.2 C of negative charge to a target in 2 seconds. How many individual electrons strike the target during this period? (e = 1.6 × 10⁻¹⁹ C)

  1. 2.0 × 10¹⁹
  2. 1.0 × 10¹⁹
  3. 3.2 × 10¹⁹
  4. 6.4 × 10¹⁹
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Answer: A

Q = n × e => n = Qe = 3.2 C1.6 × 10⁻¹⁹ C = 2.0 × 10¹⁹ electrons.

3. A current of 2.5 A flows through a bulb for 4 minutes. What total electric charge passes through the bulb?

  1. 10 C
  2. 600 C
  3. 100 C
  4. 1000 C
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Answer: B

Q = I × t = 2.5 A × (4 × 60 s) = 2.5 A × 240 s = 600 C.

4. Two resistors of resistance R and 2R are connected in SERIES across a power supply. How does the power dissipated in the 2R resistor compare to the R resistor?

  1. It is half as much.
  2. It is twice as much.
  3. It is four times as much.
  4. It is equal.
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Answer: B

In series, current I is identical. Power P = I²R. Therefore, P ∝ R. The 2R resistor dissipates twice the power of the R resistor.

5. Two resistors of resistance R and 2R are connected in PARALLEL across a DC voltage supply. How does the power dissipated in the 2R resistor compare to the R resistor?

  1. It is half as much.
  2. It is twice as much.
  3. It is four times as much.
  4. It is equal.
Show answer

Answer: A

In parallel, potential difference V is identical. Power P = V² / R. Therefore, P ∝ 1R. The 2R resistor dissipates half the power of the R resistor.

6. Three identical 10 Ω resistors are connected in SERIES to a 15 V battery. What is the potential difference across ONE of the resistors?

  1. 15 V
  2. 5 V
  3. 10 V
  4. 1.5 V
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Answer: B

Total resistance R = 10 + 10 + 10 = 30 Ω. Current I = 1530 = 0.5 A. Voltage across one resistor V = I × R_i = 0.5 A × 10 Ω = 5 V.

7. In a V against I graph obtained for a cell, the vertical y-intercept represents:

  1. The total external resistance
  2. The electromotive force (e.m.f.) of the cell
  3. The internal resistance of the cell
  4. The short-circuit current
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Answer: B

From V = E - Ir, when I = 0 (open circuit / y-intercept), V = E (the electromotive force).

8. Superconductors are unique materials that exhibit:

  1. Infinite resistance at room temperature
  2. Zero electrical resistance below a critical transition temperature (Tc)
  3. Zero potential difference regardless of current
  4. Constant current output under changing magnetic fields
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Answer: B

Superconductors lose all electrical resistance (R = 0) when cooled below their specific critical temperature (Tc).

9. What is the unit of electrical resistivity ρ?

  1. Ω
  2. Ω m
  3. Ω m⁻¹
  4. W m⁻¹
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Answer: B

From R = ρ(lA), ρ = R × Al => Ω × m² / m = Ω m (ohm-meter).

10. Which change will DOUBLE the resistance of a cylindrical uniform copper wire?

  1. Doubling the radius of the wire
  2. Doubling the cross-sectional area of the wire
  3. Doubling the length of the wire
  4. Halving the length of the wire
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Answer: C

From R = ρ(lA), resistance R is directly proportional to length l. Doubling l doubles the resistance.

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