An electric room heater is used to provide warmth in a home.
State the region of the electromagnetic spectrum which radiates thermal energy from the heater.
Explain why the polished silver-colored surface behind the heating elements increases the thermal energy radiated into the room.
The metal outer casing of the heater is connected to an earth wire. State why this is an important safety feature.
The mains voltage is 240 V240\text{ V}240 V. The two identical heating elements are connected in parallel. Each heating element has a resistance of 75 Ω75\ \Omega75 Ω.
Calculate the current in one heating element.
Show that the electrical power of the heater is approximately 1500 W1500\text{ W}1500 W. State any equation you use in words or symbols.
The heater is 92%92\%92% efficient at converting electrical work done into useful thermal energy. Calculate the useful thermal energy emitted by the heater in 90 s90\text{ s}90 s. Give your answer to two significant figures.
452 exam-style questions on CIE IGCSE Physics 4.2 Electrical quantities, covering 4.2.1a Positive and negative charge, 4.2.1b Charging by friction and detecting charge, 4.2.1c Electrical conductors and insulators, 4.2.1d Electric fields and electric field patterns, 4.2.2a Electric current, charge and measuring current, 4.2.2b Conduction in metals and the direction of current, 4.2.2c Direct current and alternating current, 4.2.3a Electromotive force, 4.2.3b Potential difference and voltmeters, 4.2.4a Resistance, 4.2.4b Resistance of a metallic wire, 4.2.4c Current–voltage graphs, and 4.2.5 Electrical energy and electrical power. Each one has a worked solution and a mark scheme showing where the marks go.