Investigating Energy Efficiency

Name:

Date:

📚 Part 1: Quick concept check

1. Which choice best describes energy efficiency?

The amount of energy wasted in a system

The ratio of useful energy output to total energy input

Energy measured in volts and amps only

The total energy stored in a device

2. Check all that apply: Common causes of energy loss in experiments include:

Heat dissipated to the environment

Electrical resistance in wires

Perfect conversion of all input energy

Measurement instrument error

3. In one sentence, state the law of conservation of energy as used in these investigations:

✏️ Part 2: Practical calculations

4. Electrical experiment: You connect a 9 V battery to a bulb. Measured current is 0.50 A. Over 60 s, the bulb's voltage drop is 6.0 V. Calculate:

a) Total electrical energy supplied by the battery (J) = ________

b) Useful electrical energy delivered to the bulb (J) = ________

c) Efficiency of the bulb (%) = ________

5. Thermal experiment: 200 g of water is heated from 20°C to 60°C. (Use specific heat capacity of water = 4180 J·kg⁻¹·°C⁻¹.)

a) Useful thermal energy gained by the water (J) = ________

b) If the heater supplied 42 000 J, calculate efficiency (%) = ________

6. Safety: List two precautions for electrical work and two precautions for heating experiments (one short phrase each):

🔍 Part 3: Analyse, reflect & extend

7. Identify two possible sources of error in the electrical experiment and one practical way to reduce each error:

8. Suggest one extension investigation (change a variable) to deepen understanding of efficiency. Describe the variable you would change and the expected insight in one sentence:

9. Draw a simple Sankey diagram for the thermal experiment (show energy input, useful output and losses). Label percentages or relative widths if possible: