CIE iGCSE Co-Ordinated Science P2.3.1 Conduction Exam Style Questions Paper 3

(a) fuse symbol inserted in the gap in the circuit

A fuse is normally placed in the live wire of a mains circuit, close to the supply.
The standard fuse symbol (a rectangle on the wire) should be drawn in the gap shown in Fig. 12.1.

(b)(i) resistance = 80 Ω

Resistance is calculated using \(R = \dfrac{V}{I}\).
\(R = \dfrac{240}{3} = 80\,\Omega\).

(b)(ii) a fuse must have a rating slightly higher than the normal operating current

The heater draws a normal current of \(3\,\text{A}\).
A \(3\,\text{A}\) fuse would blow during normal use, so a \(5\,\text{A}\) fuse (just above the operating current) is chosen instead, so it only blows if the current becomes dangerously high.

(c)(i) conduction

Thermal energy passes through the solid floor material by conduction.
This is because conduction is the main method of thermal energy transfer through solids.

(c)(ii) convection

Air heated near the floor becomes less dense and rises, while cooler air sinks to take its place.
This circulation of air, known as convection, spreads thermal energy throughout the room.

(d) faster-moving (most energetic) molecules escape from the surface of the liquid

In the water, molecules move with a range of different speeds.
The fastest-moving, most energetic molecules near the surface have enough energy to overcome the forces holding them in the liquid and escape as vapour, which is evaporation.

(e) advantage: renewable / does not produce carbon dioxide; disadvantage: only works during daylight / needs sunlight

Solar cells generate electricity using a renewable energy source and produce no carbon dioxide during operation.
However, they only generate electricity when sunlight is available, so output depends on daylight and weather conditions.