ELECTRONIC PRINCIPLES - OD1647 - LESSON 1/TASK 1
illustrated in figure 51. Notice that one white arrow plus one
striped arrow comprise one coulomb.
1. Disadvantages of DC (Compared to AC. When commercial use of
electricity became widespread in the United States, certain
disadvantages in using direct current in the home became
apparent. If a commercial direct current system is used, the
voltage must be generated at the level (amplitude or value)
required by the load. To properly light a 240 volt lamp, for
example, the dc generator must deliver 240 volts. If a 120 volt
lamp is to be supplied power from the 240 volt generator, a
resistor or another 120 volt lamp must be placed in series with
the 120 volt lamp to drop the extra 120 volts. When the
resistor is used to reduce the voltage, an amount of power equal
to that consumed by the lamp is wasted.
FIGURE 51. COMPARING DC & AC CURRENT FLOW IN A WIRE.
Another disadvantage of the direct current system becomes
evident when the direct current (I) from the generating station
must be transmitted a long distance over wire to The consumer.
When this happens, a large amount of power is lost due to the
resistance (R) of the wire. The power loss is
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