CIE iGCSE Co-Ordinated Science P2.3.1 Conduction Exam Style Questions Paper 4
Question
(a) Describe how thermal energy passes through copper by conduction.
▶️Answer/Explanation
Thermal energy is transferred through copper via the vibration of atoms. These vibrations are passed from one atom to neighboring atoms. Additionally, delocalized electrons in the metal carry energy through the material, contributing to efficient heat transfer.
(b) Copper boils at 2562°C. Describe two differences between boiling and evaporation.
▶️Answer/Explanation
1. Boiling occurs at a specific temperature (boiling point) throughout the liquid, while evaporation can occur at any temperature and only at the liquid’s surface.
2. During boiling, bubbles of vapor form within the liquid, whereas evaporation involves molecules escaping from the surface without bubble formation.
(c) Equal volumes of air, copper and water are heated from 10°C to 90°C. State which of these materials will expand:
▶️Answer/Explanation
most – air
least – copper
(d) A copper wire of length 0.5 m has a resistance of 0.02 Ω. Determine the resistance of another copper wire of length 0.25 m that has twice the cross-sectional area.
▶️Answer/Explanation
Using the formula R = ρL/A:
Original wire: 0.02 = ρ(0.5)/A
New wire: R = ρ(0.25)/2A = (ρ(0.5)/A)/4 = 0.02/4 = 0.005 Ω
resistance = 0.005 Ω
(e) Two wires are connected in parallel. One wire has a resistance of 0.40 Ω. The other wire has a resistance of 0.60 Ω.
Calculate the combined resistance of the two wires connected together in parallel.
▶️Answer/Explanation
Using the parallel resistance formula: 1/Rtotal = 1/R1 + 1/R2
1/Rtotal = 1/0.40 + 1/0.60 = 2.5 + 1.666… = 4.166…
Rtotal = 1/4.166… ≈ 0.24 Ω
resistance = 0.24 Ω
(f) Copper wire is used in the coil of a generator. Fig. 6.1 shows a simple a.c. generator.
(i) On Fig. 6.1 label the coil with the letter C.
(ii) An electromotive force (e.m.f.) is induced in the rotating coil. State two factors that would increase the magnitude of the induced e.m.f.
▶️Answer/Explanation
(i) [The coil should be labeled with a “C” in the diagram]
(ii) 1. Increasing the speed of rotation of the coil
2. Increasing the strength of the magnetic field