Voltage Division: Introduction
to Series and Parallel Circuits
Resistors, Light Bulbs (Incandescent
Lamps) and Bungee Cords have "resistance" in common. In conventional
track lighting, all lamps are in parallel and independent of one another
in the sense that one lamp can burn out without affecting the others.
Adding another lamp merely increases the illumination, again, without affecting
In a string of "holiday"
lights, the lamps are all in series - if one lamp is removed, ALL lamps
go out. Oddly, one or more lamps can burn out and the rest stay lit
because an internal resistor is in parallel with each lamp filament.
This design allows the user to find the bad lamps before the whole string
goes out. This happens if too many lamps burn out, stressing the
hiddent resistors into failure.
The Bungee Analogy helps
to explain what it feels like to be a filament. Stretch a bungee
for as long as possible and you will warm up - that's what happenes when
electrical current flows. A filament is literally white hot when
voltage is applied to it. Imagine the ceiling and the floor as the
difference in potential voltage, let's say one-volt per foot, for a distance
of ten feet. Now, imagine an eye hook in both locations to which
a single bungee is stretched. Pretty taut, eh?
Now, connect two bungees
of equal elasticity in series between floor and ceiling.
Where do they meet? In the middle, of course, dividing 10-volts in
half. The bungees are now half as taut as one signle bungee was.
If each was a 100-watt light bulb, they'd now be operating at 50-watts.
for Voltage Division Exercise
Ohm's Law is one example
of how math can describe what happens to electrons as they make the journey
from power source to components and back It is ALWAYS a round trip,
what is referred to in wiring as Continuity.
Ohm's Law defines the relationships
between (P) power, (E) voltage, (I) current, and (R) resistance. One ohm
is the resistance value through which one volt will maintain a current
of one ampere. Students should know two primary formulae - Ohm's
Law and the Power Formula - from which they can derive all the
This image courtesy of the12volt.com