When air, the incline and/or rolling friction hinder the vehicles mobility, one speaks of 'resistance', exactly the same as when the electrons are hindered in their movement. Given the current and the voltage, one is able
to calculate the resistance. This way, the stress can also be determined. Resistors are among the cheapest components, nonetheless, their direct destruction inside the circuit, would be a pity. One can recognise a
defect by an infinitely high resistance value. The best thing to do, is to limit the maximum performance by using a low resistance of max. 0,25 W.
All the components in a circuit have a resistance. This is valid for the battery and of course, also for the cables. The cable-resistance in the vehicle, because of the mostly short lengths, must only be taken into
consideration, with components which have wire windings (e.g., coils, relays and electric motors). Should you wish to calculate these resistances, please click
here. Although the temperature of the resistor plays a very important role, it has no influence in the resistance
calculation. This is due to the fact that, in this case, it is set at 20°C.
As already mentioned, in the case of the light bulb, the temperature of the cable-resistance plays an important role. Most
cables are made of copper, a material with a positive temperature coeffient (PTC). This means, that the resistance increases with the rising temperature. Thus, by the way, the warmer the cables become, the greater
their losses are. Almost all the consumers in the automobile have this distinctive PTC-behaviour (Positive Temperature Coeffient). One good example is the glow-plug, which thereby, limits it's own current intake. Independent of the temperature, is Constantan, - as the name already indicates - an alloy
manufactured for this purpose from Cu, Ni and a little Mn.
Resistances, like the one shown above, are found in nearly all electronic circuits. The coloured rings are read from the edge to which they are closest. While the first three show the resisistance value in encoded form,
the fourth shows the tolerance with which this value is held. 11/10
1 M = 1.000 k = 1.000.000