Circuit diagrams and circuit components — Draw

Draw and interpret circuit diagrams using standard symbols for components such as cells, batteries, switches, resistors, thermistors, LDRs, lamps, motors, bells, meters, transformers, fuses and relays, and describe how each behaves in a circuit.

Students should recognise and use the standard IGCSE circuit symbols and know each component's behaviour: a cell/battery supplies e.m.f.; a switch opens/closes the circuit; a fixed resistor has constant resistance; a variable resistor (rheostat) allows resistance (and so current) to be adjusted; an NTC thermistor's resistance decreases as its temperature increases; an LDR's resistance decreases as light intensity increases; a lamp lights up and has resistance that increases with temperature; a motor converts electrical energy to kinetic energy; a bell uses an electromagnet to strike repeatedly; an ammeter (very low resistance) is placed in series to measure current; a voltmeter (very high resistance) is placed in parallel to measure p.d.; a magnetising coil produces a magnetic field when current flows; a transformer changes a.c. voltage using two coils on an iron core; a fuse melts to break the circuit if current is too large; and a relay uses a small current in an electromagnet to switch a separate, often larger-current, circuit.