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