Electricity and Circuits

An electric circuit is a closed path through which current can flow. Components: cell/battery (source of electrical energy), wire (conductor), bulb (load), switch (control). Current flows from positive terminal of cell, through circuit, back to negative terminal. Circuit must be CLOSED (complete) for current to flow.

Cell: device that converts chemical energy to electrical energy. Has positive (+) and negative (-) terminals. Battery: two or more cells connected. When cells connected in series (+ to -): voltages add. The liquid or paste inside cell is the electrolyte. Cell symbol: long line (+) and short thick line (-).

Conductors: allow current to pass through. Most metals: copper, iron, aluminium, silver. Graphite (pencil lead) also conducts. Insulators: do not allow current. Plastic, rubber, wood, glass, cloth. Uses: copper wires carry current; plastic covering insulates and protects from shocks.

Switch: controls the flow of current. Open switch = broken circuit = no current. Closed switch = complete circuit = current flows. Fuse: a safety device — thin wire that melts if too much current flows, breaking the circuit and preventing fire/damage. Key safety principle: never touch live wires!