A Level H1 Physics Energy Power Quiz

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A-Level Physics H1 Quiz - Energy Power

Name: ______________________
Class: ______________________
Date: ______________________
Score: _______ / 40

Duration: 50 minutes
Total Marks: 40
Topic: Energy & Power (energy-power)

Instructions:

• Answer all 20 questions.
• Show your working clearly for calculation questions.
• Use the spaces provided.
• Section A: Short Answer (1–7), Section B: Structured Calculations (8–14), Section C: Data & Concept Interpretation (15–20).

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Section A: Short Answer (1–7)

1. State the principle of conservation of energy. [1]

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2. Define power in terms of energy transfer. [1]

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3. Write down the equation for kinetic energy of a mass $m$ moving at speed $v$. [1]

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4. A device transfers $200\text{ J}$ of energy in $10\text{ s}$. State its average power. [1]

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5. Define efficiency of an energy transfer process. [1]

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6. The elastic potential energy stored in a spring is given by the area under a force-extension graph. State the formula for elastic potential energy when a spring of constant $k$ is extended by $x$. [1]

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7. A crane lifts a load. State the type of energy increase of the load. [1]

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Section B: Structured Calculations (8–14)

8. A block of mass $4.0\text{ kg}$ slides down a frictionless slope from rest, dropping through a vertical height of $3.0\text{ m}$.
(a) Calculate the loss in gravitational potential energy. [2]
(b) Hence determine the speed of the block at the bottom. [2]

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9. A car engine produces $90\text{ kW}$ of power and moves the car at a constant speed of $30\text{ m s}^{-1}$. Calculate the driving force provided by the engine. [3]

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10. A $1.5\text{ kW}$ electric heater is used for $20$ minutes.
(a) Calculate the electrical energy consumed in joules. [2]
(b) If the heater is $80\%$ efficient at transferring heat to the room, calculate the heat energy delivered. [2]

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11. A student claims: "A $100\text{ W}$ bulb is more efficient than a $60\text{ W}$ bulb because it is more powerful." Explain why this statement is not necessarily correct. [3]

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12. A wind turbine has an input power from wind of $500\text{ kW}$ and outputs $150\text{ kW}$ of electrical power.
(a) Calculate its efficiency as a percentage. [2]
(b) State one reason why the remaining energy is not converted. [1]

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13. A spring of spring constant $k = 200\text{ N m}^{-1}$ is compressed by $0.10\text{ m}$. Calculate the elastic potential energy stored. [2]

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14. A pump lifts $500\text{ kg}$ of water per minute through a height of $12\text{ m}$. Calculate the minimum power of the pump. ($g = 9.8\text{ m s}^{-2}$) [3]

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Section C: Data & Concept Interpretation (15–20)

15. The graph below shows power output of a solar panel over a day.

Image pending generation: graph for Q15.

Estimate the total energy generated between 06:00 and 18:00. Show your method. [3]

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16. Describe the energy transfers that occur when a mobile phone is charged from a solar power bank. [3]

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17. A pendulum is released from a height $h$ and swings without air resistance.
(a) State the form of energy at the highest point. [1]
(b) State the form of energy at the lowest point. [1]
(c) Explain how the principle of conservation of energy applies. [2]

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18. The diagram shows a downhill cyclist.

Image pending generation: diagram for Q18.

Ignoring friction, calculate the speed at the bottom of the slope. ($g = 9.8\text{ m s}^{-2}$) [3]

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19. Compare the advantages of using a high-efficiency motor versus a low-efficiency motor in a factory. [3]

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20. A battery of EMF $12\text{ V}$ and internal resistance $0.5\ \Omega$ supplies a $5.5\ \Omega$ resistor.
(a) Calculate the current. [2]
(b) Calculate the power dissipated in the external resistor. [2]

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A-Level Physics H1 Quiz - Energy Power (Answer Key)

Topic: Energy & Power
Total Marks: 40

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Section A: Short Answer

1. [1] The total energy of an isolated system is constant; energy cannot be created or destroyed, only transferred or transformed.
Teaching note: This is the core principle. "Isolated" means no external energy input/output.

2. [1] Power is the rate of energy transfer (or rate of doing work), $P = \frac{E}{t}$.
Teaching note: Unit is watt (W) = J s⁻¹.

3. [1] $E_k = \frac{1}{2}mv^2$
Teaching note: Do not forget the $\frac{1}{2}$.

4. [1] $P = \frac{200}{10} = 20\text{ W}$
Teaching note: Direct substitution.

5. [1] Efficiency = $\frac{\text{useful output energy}}{\text{total input energy}} \times 100\%$ (or fraction).
Teaching note: Always less than 100% in real devices.

6. [1] $E = \frac{1}{2}kx^2$
Teaching note: Area under F-x graph = $\frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2}kx \cdot x$.

7. [1] Gravitational potential energy.
Teaching note: Height increases → G.P.E. increases.

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Section B: Structured Calculations

8. [4]
(a) $\Delta E_p = mgh = 4.0 \times 9.8 \times 3.0 = 118\text{ J}$ [2]
(b) By conservation: $\frac{1}{2}mv^2 = 118$ → $v = \sqrt{\frac{2 \times 118}{4.0}} = 7.7\text{ m s}^{-1}$ [2]
Marking: [2] for (a) correct sub and ans; [2] for (b) method and ans.

9. [3]
$P = Fv$ → $F = \frac{P}{v} = \frac{90\,000}{30} = 3000\text{ N}$ [3]
Note: Convert kW to W: $90\text{ kW} = 90\,000\text{ W}$.

10. [4]
(a) $t = 20 \times 60 = 1200\text{ s}$; $E = Pt = 1500 \times 1200 = 1.8 \times 10^6\text{ J}$ [2]
(b) $E_{\text{heat}} = 0.80 \times 1.8 \times 10^6 = 1.44 \times 10^6\text{ J}$ [2]

11. [3]
Efficiency depends on useful output per input, not absolute power [1]. A 100 W bulb may give more light but could waste more energy as heat than a 60 W bulb [1]. Without knowing lumen output or input, power alone does not show efficiency [1].

12. [3]
(a) $\eta = \frac{150}{500} \times 100\% = 30\%$ [2]
(b) Energy lost to sound, heat, or motion of air [1].

13. [2]
$E = \frac{1}{2}kx^2 = 0.5 \times 200 \times (0.10)^2 = 1.0\text{ J}$ [2]

14. [3]
$m = 500\text{ kg}$ per min → per sec: $500/60 = 8.33\text{ kg s}^{-1}$
$P = \frac{mgh}{t} = (8.33) \times 9.8 \times 12 = 980\text{ W}$ [3]
Alternative: $E = mgh = 500 \times 9.8 \times 12 = 58\,800\text{ J}$ per 60 s → $P = 980\text{ W}$.

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Section C: Data & Concept Interpretation

15. [3]
Energy = area under P-t graph ≈ trapezium/triangle: approx $\frac{1}{2} \times 12\text{ h} \times 3.5\text{ kW} = 21\text{ kWh}$ [2]; convert if needed: $21 \times 3.6\times10^6 = 7.56\times10^7\text{ J}$ [1].
Image needed: curve as described; area = estimate.

16. [3]
Solar → chemical (power bank) [1]; chemical → electrical (phone battery) [1]; electrical → chemical (phone storage) + heat [1].

17. [4]
(a) Gravitational potential energy [1]
(b) Kinetic energy [1]
(c) At top all energy is G.P.E.; at bottom it is K.E.; total constant if no air resistance [2].

18. [3]
$mgh = \frac{1}{2}mv^2$ → $v = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 5} = 9.9\text{ m s}^{-1}$ [3]
Image: slope with h and m labels as given.

19. [3]
High-efficiency: less energy wasted as heat [1], lower running cost [1], less environmental impact [1]. Compare directly with low-efficiency opposite points.

20. [4]
(a) $R_{\text{total}} = 0.5 + 5.5 = 6.0\ \Omega$; $I = \frac{12}{6.0} = 2.0\text{ A}$ [2]
(b) $P = I^2R = (2.0)^2 \times 5.5 = 22\text{ W}$ [2]