Edexcel iGCSE Physics (4PH1) 4.1 Units Exam Style Question Paper 1B - New Syllabus

Edexcel iGCSE Physics (4PH1) Paper 1B - All Chapters

Question 

The diagram shows a small computer in two different cases, X and Y. The electronic chip in the computer is hot when in use. Each case is designed to cool the computer chip.

Case X is made of white plastic and has a fan.
Case Y is made of black-painted aluminium metal and has no fan. There is a metal block that is in contact with the case and the chip.

(a) Explain the main method of heat transfer from the chip to the surroundings for case X.

(b) Explain the main method of heat transfer from the chip to the surroundings for case Y.

(c)(i) State the formula linking power, current and voltage.

(ii) The small computer operates at a voltage of \(5.1\,\mathrm{V}\) with a current of \(2.9\,\mathrm{A}\). Calculate the power of the small computer. Give the unit.

Syllabus Topic Codes (Edexcel International GCSE Physics 4PH1):

• 4.6–4.8: Thermal Energy Transfer, Convection, Radiation, Absorption, and Emission — parts (a) and (b)
• 4.10: Reducing Unwanted Energy Transfer — parts (a) and (b)
• 2.4–2.5: Power, Current, Voltage, and Electrical Energy Transfer — part (c)
• 4.1: Power, Current, Voltage, and Electrical Energy Transfer — part (c) (ii)
▶️ Answer/Explanation

(a) Case X: heat transfer [3 marks]

  • The main method of heat transfer is convection.
  • The fan helps the air circulate, increasing the rate of convection and carrying thermal energy away from the chip.
  • Plastic and air are relatively poor conductors of thermal energy, so conduction is not the main method of heat transfer.

The white plastic is also a relatively poor emitter of infrared radiation, so convection is the main method in this case.

(b) Case Y: heat transfer [3 marks]

  • The main method of heat transfer from the chip to the case is conduction.
  • Aluminium is a good conductor of thermal energy, so thermal energy passes efficiently from the chip through the metal block and case.
  • Convection is not the main method because hot air inside the case cannot circulate freely from the chip to the outside.

The black-painted surface is also a good emitter of infrared radiation, helping thermal energy transfer from the case to the surroundings.

(c)(i) Formula for power [1 mark]

The formula linking power, voltage and current is:

\(\boxed{P=VI}\)

(c)(ii) Power of the computer [3 marks]

Use:

\(P=VI\)

Substitute \(V=5.1\,\mathrm{V}\) and \(I=2.9\,\mathrm{A}\):

\(P=5.1\times2.9\)

\(P=14.79\,\mathrm{W}\)

Rounding appropriately:

Therefore: \(\boxed{P\approx15\,\mathrm{W}}\)

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