Voltage source

A laboratory power supply converts energy from the mains into a steady, adjustable DC voltage at its output. The voltage source symbol is a circle with + and − marks. Many bench supplies can also limit the current to protect the circuit.

Set a suitable voltage and current limit before connecting a circuit. A bench supply needs an external energy source; a battery uses stored chemical energy.

Sparkie sets the workshop supply to 5 V to test a lantern circuit, then keeps its current limit low while checking the wiring.