A household receives an electricity bill that lists energy consumption in kilowatt-hour (kWh), while the ratings printed on individual appliances are in watt (W) or kilowatt (kW).
(i) Distinguish between watt and kilowatt-hour as physical quantities.
(ii) Explain why the kilowatt-hour is preferred over the joule for commercial measurement of electrical energy.
(iii) A table lamp is marked "100 W". State whether this value represents power or energy and justify your answer briefly.