For the passage of electric current needed closed circuit. It consists of a source (eg, battery), consumers (lamps, starter) and wires that are connected to a current source and consumers.
Tension - a potential difference, measured in volts (V).
Amperage characterizes the amount of electric charge transferred through the cross section of the conductor per unit of time, measured in ampere (A).
Power - the product of voltage and current, which shows how the electrical power source makes the work with respect to the consumer, measured in watts (W).
Resistance, which renders electric circuit (conductor) moving electric charges therein. This ratio of the voltage applied to the resistance to a current flowing through the resistance unit - ohms.
Wire. Wire thickness (the sectional area) is dependent on the consumer. For a control lamp is sufficient cross-section of 0.5 mm2 for a starter is required wire cross-section of 16 mm2. Too thin wire may overheat, causing voltage drops. In this case, the range to, for example, does not reach 12, and 10, or even 9.5 V. As a result, the lights will dim.