Electric Circuit
Definition
A complete loop that lets charge flow — a path from a power source, through components, and back again.
Technical definition
A closed conducting path in which charge can circulate, comprising a source of EMF, conductors, and loads. Kirchhoff's laws govern it: charge is conserved at junctions and energy per charge is conserved around loops.
Example
A flashlight is the simplest useful circuit: battery → switch → bulb filament → back to battery. Flip the switch open and the loop breaks — current stops everywhere at once, not just 'after' the switch.
A circuit must be a closed loop. One wire from a battery to a bulb does nothing — charge needs a return path. This is also why birds can sit safely on a high-voltage line: with no path through their bodies back to ground, no current flows through them. Break the loop anywhere and everything stops, everywhere, at once.