AQA GCSE Physics Physics Paper 1 (Foundation), June 2025: Question 5

✅ Mark Scheme Answers

• Earth wire: green and yellow [1 mark]
• Live wire: brown [1 mark]
• Neutral wire: blue [1 mark]

💡 Easy Memory Mnemonics

• bLue = Left (Neutral, 0 V)
• bRown = Right (Live, carries 230 V alternating potential)
• Striped Green & Yellow = Top (Earth, safety wire connected to metal casing)

🧠 Exam Technique

Always double-check the provided list in the box. Do not write "yellow and green" if the option given is "green and yellow", and never write "red" or "black" — those are obsolete UK/international colours replaced decades ago!

❌ Common Errors

• Swapping live (brown) and neutral (blue).
• Selecting single colours like "yellow" or "green" instead of the dual colour "green and yellow" for earth.

✅ Correct Answer

Option 3 (Bottom Box): A rectangle with the connecting wire passing straight through the middle.

💡 Distinguishing the Symbols

• Symbol 1 (Top): Circle with incoming arrows = LDR (Light Dependent Resistor).
• Symbol 2 (Middle): Resistor with a hockey stick line = Thermistor.
• Symbol 3 (Bottom): Rectangle with line running completely through = Fuse.

❌ Common Traps

Students often confuse a fixed resistor (wire terminates at edges of rectangle) with a fuse (wire passes completely through the centre of the rectangle).

📐 Step-by-Step Calculation

Given values:

• Power, P = 2420 W
• Current, I = 11.0 A

Step 1: Substitute into the given formula:

potential difference = power / current

V = 2420 / 11.0 [1 mark]

Step 2: Calculate the numerical value:

V = 220 V [1 mark]

🧠 Exam Technique & Reality Check

UK mains voltage is nominally 230 V. A calculated value of 220 V is realistic for a domestic appliance under load. If your calculation yields 26,620 or 0.0045, you multiplied instead of dividing!

📐 Step-by-Step Calculation

Given values:

• Power, P = 2420 W
• Current, I = 11.0 A

Step 1: Substitute into the equation:

resistance = power / (current)²

R = 2420 / (11.0)² = 2420 / 121 [1 mark]

Step 2: Solve:

R = 20 Ω [1 mark]

❌ Common Calculation Traps

• Forgetting to square: Calculating 2420 / 11 = 220 instead of 2420 / 11² .
• Squaring the fraction: Typing (2420 / 11)² into the calculator instead of 2420 / (11²) .

🧠 Alternative Method Check

From part 05.3, you know V = 220 V and I = 11.0 A . Using Ohm's Law: R = V / I = 220 / 11.0 = 20 Ω . Checking this gives you instant confidence that both answers are correct!

✅ Correct Selections (Tick Two)

• ☑ Statement 1: A greater percentage of energy is usefully transferred by kettle A. [1 mark]
• ☑ Statement 3: Kettle A takes less time to boil the same volume of water. [1 mark]

💡 The Physics of Efficiency

Efficiency = Useful Energy Output / Total Energy Input

• Both kettles receive the same total power input.
• Higher efficiency means Kettle A converts a higher proportion of that input into thermal energy in the water.
• Because useful power output is higher, Kettle A heats the water faster and takes less time to reach 100 °C.
• Kettle A wastes less energy to the surroundings, not more.

❌ Why the Other Statements Are Incorrect

• "Kettle A has a lower useful power output" — False: Greater efficiency at the same total input means higher useful output.
• "More energy is wasted by kettle A each second" — False: Kettle A is more efficient, so it wastes less energy.
• "The temperature of the same volume of water increases more slowly in kettle A" — False: With more useful energy transferred per second, temperature rises faster.