Question 1: Define the term 'efficiency' in the context of energy transfers.

Answer: Efficiency is a measure of how much useful energy is transferred or converted compared to the total energy supplied, expressed as a percentage.

Question 2: Explain why no energy transfer process is 100% efficient.

Answer: Because some energy is always lost to the surroundings as heat, sound, or other forms of non-useful energy during transfer or conversion processes.

Question 3: What is the formula to calculate the efficiency of a machine?

Answer: Efficiency = (Useful energy output / Total energy input) × 100%

Question 4: A car engine consumes 100 kJ of fuel energy and produces 30 kJ of useful work. Calculate the efficiency of the engine.

Answer: Efficiency = (30 / 100) × 100% = 30%

Question 5: A light bulb has a power consumption of 60 W but only produces useful light energy at an efficiency of 10%. How much useful energy does it produce in 1 hour?

Answer: Useful energy = Power × Time × Efficiency = 60 W × 3600 s × 0.10 = 21,600 J

Question 6: Identify two variables that can affect the efficiency of a heat engine.

Answer: Temperature difference between the hot and cold reservoirs, and the quality of the engine components.

Question 7: Describe a practical experiment to measure the efficiency of a pulley system.

Answer: Set up the pulley with a known mass and measure the input work done to lift the mass a certain height. Measure the useful work output by calculating the gravitational potential energy gained by the load. Calculate efficiency using the formula: (useful work / work input) × 100%. Ensure safety by securing all components and handling weights carefully.

Question 8: A wind turbine converts wind energy into electrical energy with an efficiency of 45%. If the wind supplies 500 kJ of energy, how much electrical energy is generated?

Answer: Electrical energy = 500 kJ × 0.45 = 225 kJ

Question 9: Explain how improving the insulation of a building can increase its overall energy efficiency.

Answer: Better insulation reduces heat loss to the surroundings, meaning less energy is required to maintain a comfortable temperature, thereby increasing overall efficiency.

Question 10: Describe one technological advancement that has improved energy efficiency in industry.

Answer: The development of high-efficiency electric motors that convert electrical energy into mechanical work with minimal energy loss.

Question 11: In your own words, explain why efficiency is an important concept in modern engineering and technology.

Answer: Efficiency is crucial because it determines how well energy is utilised, helping to reduce waste, lower costs, and minimise environmental impact. Improving efficiency in engineering and technology leads to sustainable development and better resource management.