Alternating Current And Direct Current - Honda Motorcycle Service Manual

ELECTRICAL FUNDAMENTALS
ALTERNATING CURRENT AND DIRECT CURRENT
All electrical components are supplied with either alternating
current or direct current, abbreviated as AC or DC respectively.
The fundamental characteristic of the two currents differ
completely. and for the purpose of servicing, you need to have
a good understanding of these differences.
Alternating current (ACI changes in voltage value and polarity
with time. AC current flows in one direction until peak voltage
is reached and then drops to zero volts. AC current then
changes direction or polarity until peak voltage is achieved and
again drops to zero and again changes polarity. From zero
voltage to peak positive voltage to peak negative voltage and
back again to zero voltage is known as a cycle.
In motorcycles, all electricity generated is AC. However, AC
can be converted to direct current (DC) by rectification. The
DC current is then supplied to components operating on DC.
For example, some models use DC for their headlights and
others use AC.
For headlights operating on AC, the lights turn off when the
current flow is zero, and then go back on again as the polarity
becomes reversed. This ON-OFF cycle is repeated at a high fre-
quency (number of cycles in one second) and is not noticable.
ALTERNATING CURRENT
0
f
0
0
TIME
Direct current is a current whose magnitude and direction re-
main constant. Its form is shown in the graph. Direct current is
1
f
Direct current
abbreviated as DC. Motorcycle batteries, and household bat-
teries supply DC.
DIRECT CURRENT
\
CURRENT
DC has the following characteristics as opposed to AC.
i " 7 .Pi!%
.
DC can be storedjn batteries and discharged when needed.
(AC cannot be stored)
.
DC is capable of a large current flow. (Good for starter
motors)
.
DC voltage cannot be stepped up or down.(AC voltage can
be changed using a transformer)
Date of Issue: March, 1995
0
HONDA MOTOR CO.,LTD.
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