As shown below, all automotive electrical circuits have one or more of the following components: Power Source - Battery, Alternator, Capacitor, etc. Circuit Protection - Fuse, fusible link, Circuit Breaker. Control Device - Switch, switched on the power side or the ground side of the circuit. A Current path - Wire Electrical Load - Relay, Solenoid, light bulb, motor, etc. Ground path - leading to the battery negative post.