An electrical power grid transmits 120 MW120\text{ MW}120 MW of power from a power station to a substation through transmission cables with a total resistance of 8.0 Ω.
Calculate the power lost as heat in the transmission cables if the power is transmitted at a voltage of 240 kV240\text{ kV}240 kV.
Explain, using the relevant formulas, why using a high voltage of 240 kV240\text{ kV}240 kV is preferable to a lower voltage (such as 120 kV120\text{ kV}120 kV) for transmitting electrical power over long distances.
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.