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#67 Electrical voltage drops
Voltage losses
The formula also shows that the The starter motor, ignition coil,
smaller the resistor of the "real wiper motor and headlights are
consumer", the more the other such low resistance consumers.
unwanted resistors will take volt- With the ignition coil we speak of
age away from the battery volt- a primary winding with an aver-
age. If the consumer would have age resistance of 4 Ω (therefore
a resistance of barely 4 Ω , this the example on the left with 4 Ω).
consumer would get less than
10 V: The starter motor and the igni-
tion coil need the full battery
U = 12V x (4,0 Ω / 5,1 Ω) voltage to function properly. It
bulb
is therefore very important that
U = 9,41 V the connections between bat-
bulb
tery and consumers are in good
After all, this is an important condition and offer as little resis-
lesson to use in the workshop. tance as possible. What you want
Each resistor connected in series is for the full 12 V or 6 V to reach
with the consumer will remove the consumers. All electrical re-
part of the battery voltage. The sistances in the list on the previ-
smaller the resistor of the con- ous page, except for the "real"
sumer, the worse the problem consumer, should be eliminated.
will be (read, the lower the volt- In other words, all unwanted
age across this consumer). resistors should be reduced to
zero, as far as possible.
12 Paruzzi Magazine 23
