Memory SNC1D - Drawing Circuit SymbolsVersion en ligne Drawing symbols for circuits. par Ms. S Munawar Switch: opens and closes the circuit. Resistor: general load, converts electricity to heat. Voltmeter: measures voltage. Connected in parallel. Lamp/light bulb: specific load, converts electricity to light and heat. Ammeter: measures current, Connected in series. Wire: conductor, allows electrons to flow. Fuse: Safety device that has a metal conductor which melts at high, dangerous current levels. Battery: electrical energy source.