CIE iGCSE Co-Ordinated Science P2.2.1 Thermal expansion of solids, liquids and gases Exam Style Questions Paper 4
Question
(a) Fig. 12.1 shows a truck crossing a bridge.
The bridge is designed with gaps in the road surface as shown in Fig. 12.2.
The temperature of the road surface increases on a hot day.
(i) Describe what happens to the gaps in the road surface when the temperature increases. Explain your answer.
▶️Answer/Explanation
1. Observation: Gaps become narrower as the road expands
2. Explanation: Thermal expansion causes metal/road materials to increase in length (ΔL = αLΔT)
Engineering details: – Typical steel expansion coefficient (α) = 12×10-6 °C-1 – A 50m bridge expands ~6cm when heated 100°C
(ii) Suggest what may happen to the bridge if there were no gaps in the road surface.
▶️Answer/Explanation
The bridge would buckle/warp/crack from thermal stress
Structural impact: – Compression forces can exceed 70 MPa – May cause joint failures or pavement blowouts
(b) Fig. 12.3 shows the fuel tank of the truck being filled with diesel fuel.
Explain why the diesel fuel becomes positively charged.
▶️Answer/Explanation
1. Mechanism: Friction between fuel and pipe transfers electrons
2. Result: Fuel loses electrons → becomes positively charged
Safety note: – Requires grounding to prevent sparks – Flow rates kept below 7 m/s to minimize charge
(c) The truck has a warning triangle to alert other drivers. Fig. 12.4 shows the warning triangle.
Many tiny prisms are contained in the warning triangle.
Fig. 12.5 shows one ray of light entering a prism.
The ray undergoes total internal reflection inside the prism.
Complete Fig. 12.5 to show the path of the ray of light through the prism and the ray of light leaving the prism.
▶️Answer/Explanation
1. First surface: Refraction entering prism
2. Second surface: Total internal reflection (critical angle ~42° for glass)
3. Third surface: Refraction exiting parallel to incident ray
Optical principle: – Retroreflection returns light to source – Works for wide range of incident angles
(d) The truck has a generator. Fig. 12.6 shows a simple generator producing an alternating voltage.
(i) On Fig. 12.6, label the coil C.
(ii) On Fig. 12.6, label the slip rings S.
(iii) Describe how turning the coil induces an alternating voltage.
▶️Answer/Explanation
(d)(i) coil correctly labelled ;
(d)(ii) slip rings correctly labelled ;
(d)(iii) magnetic field ;
rotating coil cuts magnetic field or flux / experiences a changing magnetic field ;
e.m.f. / current reverses every half turn ;