Battery (cell)Pushes the current round the circuit. Its circuit symbol is a long line and a short line.
WireA conductor that carries the current between the parts. The loop must be unbroken.
SwitchOpens or closes the circuit. Open, it breaks the loop and the current stops.
Bulb (lamp)A load that turns electrical energy into light. Its symbol is a circle with a cross.
ResistorResists the current, limiting how much flows; its symbol is a zigzag.
Other 3
Positive terminalThe high-potential end of the battery, marked +.
Negative terminalThe low-potential end of the battery, marked -; electrons leave from here.
CurrentThe flow of charge. By convention it leaves the positive terminal and returns to the negative.
How this list was compiled: Read 2026-09-26. (1) OpenStax Physics, 19.1 Ohm's Law, https://openstax.org/books/physics/pages/19-1-ohms-law : a battery has two terminals at different potentials; a conducting wire between them lets current flow; electrons move from the negative terminal through the wire to the positive terminal; resistors; circuit diagrams. (2) OpenStax Physics, 19.2 Series Circuits, https://openstax.org/books/physics/pages/19-2-series-circuits : batteries, wires, switches, light bulbs and resistors in series; circuit diagrams with their symbols. (3) Wikipedia, Electrical network, https://en.wikipedia.org/wiki/Electrical_network (voltage sources, resistors, switches, loads) and Circuit diagram, https://en.wikipedia.org/wiki/Circuit_diagram (standard symbols joined by lines for wires). Licence: own work
The drawing: Drawn for this site by script, 2026-09-26. Own work, nothing traced. Licence: own work
How it works
These are the parts of a circuit on one simple series circuit, drawn twice: as a picture and as a circuit diagram. Each part lights up in both, so you learn its symbol at the same time.
Read the full guide
The loop
The battery pushes current out of its positive terminal, through the wires, and back into its negative terminal. The loop must be unbroken: open the switch and the current stops.
The symbols
In a circuit diagram the battery is a long line and a short line, the switch a gap with a bar across it, the bulb a circle with a cross, and the resistor a zigzag. Straight lines are the wires.
The arrows show conventional current, from + to -. The electrons themselves move the other way.
Questions and answers
What are the basic parts of a circuit?
A source of energy such as a battery, wires to carry the current, a load that uses it such as a bulb, and usually a switch to open and close the loop.
What does a resistor do in a circuit?
It resists the flow of current, limiting how much flows. In a circuit diagram it is drawn as a zigzag.
Which way does current flow?
By convention, current flows out of the battery's positive terminal and back into its negative terminal. Electrons, which carry the charge in a wire, move from negative to positive.