Basic concepts of electrical engineering

Electric current flows only through a closed electrical circuit. Electrical circuits consist of a current source (battery, generator), consumers (incandescent lamp, starter, electric motor) and bundles of cables, consisting of countless wires. Cable bundles create the necessary connections between the power source and the consumer. The basic concept of electrical engineering is explained by our example: imagine a water pipe through which a certain amount of water flows under a certain pressure from A (current source) to B (consumer). The same thing happens in the electrical circuits of your Focus. For example, when the light comes on when the door is opened.

Voltage: it corresponds to the pressure in the water supply. Voltage unit volt (IN). Current: corresponds to the amount of water that flows through the plumbing in a certain amount of time. Current unit ampere (A).

Power: The product of voltage and current shows how much work the consumer will do from the electricity of the current source. Power unit watt (Tue).

Resistance: comparable to a water shut-off valve. When the faucet is open, the water in the pipe flows freely (resistance is 0). If the faucet is closed, the resistance gradually increases until the water stops flowing altogether (resistance about»). Resistance unit ohm (Ohm).

Wires: comparable to plumbing pipes. Required wire thickness (cross section) depends on the consumer. The control lamp is supplied with a wire thickness of 0.5 mm². The starter needs a 16mm cable² - in our example this would correspond to the connection to the main fairway. Too thin wire heats up, the voltage inevitably drops. Then, for example, not 12 V is supplied to the headlight, but only 10 or 9.5 V - sows becomes dim.