An electricity distribution company needs to transmit electrical power from a wind farm to a distant city. Which type of current is typically used in the main transmission grid, and why is a high voltage preferred?
Alternating current; high voltage reduces transmission current, decreasing thermal energy losses (I2RI^2 RI2R) in the cables.
Alternating current; high voltage increases transmission current, allowing faster power delivery.
Direct current; high voltage lowers the resistance of the cables.
Direct current; low voltage minimizes power loss by reducing the current flowing through grid lines.
275 exam-style questions on CIE IGCSE Physics 4.5 Electromagnetic effects, covering 4.5.1a Electromagnetic induction, 4.5.1b Direction of an induced e.m.f., 4.5.2 The a.c. generator, 4.5.3a Magnetic effect of a current and its applications, 4.5.3b Strength and direction of the field around wires and solenoids, 4.5.4a Force on a current-carrying conductor, 4.5.4b Force on beams of charged particles, 4.5.5 The d.c. motor, 4.5.6a Construction and operation of a transformer, 4.5.6b Turns ratio and current in a transformer, and 4.5.6c High-voltage transmission of electricity. Each one has a worked solution and a mark scheme showing where the marks go.