An instant hot water dispenser is used in an office kitchen to supply boiling water. Cold water passes over an electric heating element inside the dispenser. The boiling point of water is 100∘C100^\circ\text{C}100∘C.
State what is meant by boiling point.
The heating element is powered by the mains supply at a voltage of 240 V240\text{ V}240 V. When the dispenser is activated, the current in the heating element is 12 A12\text{ A}12 A.
Calculate the thermal energy produced by the heating element in 50 s50\text{ s}50 s.
The specific heat capacity of water is 4200 J/(kg∘C)4200\text{ J}/(\text{kg}^\circ\text{C})4200 J/(kg∘C). The cold water enters the dispenser at 20∘C20^\circ\text{C}20∘C.
Calculate the rate at which water at its boiling point emerges from the dispenser.
The dispenser has a metal casing which is earthed, and there is a fuse in the cable connecting the heating element to the mains.
Explain how the earth wire protects the user.
Explain how the fuse protects the circuit.
528 exam-style questions on CIE IGCSE Physics 2.2 Thermal properties and temperature, covering 2.2.1 Thermal expansion of solids, liquids and gases, 2.2.2a Internal energy and temperature, 2.2.2b Specific heat capacity, 2.2.3a Melting, boiling, condensation and solidification, 2.2.3b Evaporation, and 2.2.3c Cooling by evaporation. Each one has a worked solution and a mark scheme showing where the marks go.