| Inductors |
| You know that one coil can induce an Emf
into a neighboring coil. It also happens that one coil
can induce an Emf into itself, called "self-inductance".
These single coils or "inductors" are commonly
used in circuit applications.
|
 |
| Like resistors and capacitors, inductors
for circuit use come in many shapes and sizes. Typically,
all they are is a coil of wire wound into a solenoid or
a torroid. What inductors do is slow down voltage changes
in a circuit --- they act as the electrical analog to
"inertia". Just like a heavy mass resists motion,
an inductor resists voltage change. If an applied voltage
goes from zero to a maximum instantaneously, the inductor
will ensure that the circuit voltage rises slowly to the
maximum voltage. |
| Transformers |
 |
A very common application of inductors and
how one coil can induce an Emf into a neighboring coil
is the transformer. Transformers are everywhere, for instance
in the power supply for your Laptop. By inductance, transformers
can take a high voltage and "step it down" to
a low voltage, or take a low voltage and "step it
up" to a high voltage. This is all done by varying
the number of turns in each of the two coils and the Emf
induced. |
|
Transformers also allow electricity to be transmitted
great distances from the power plant to your wall socket
by boosting the voltage very high. Why? When "transformed",
if the voltage is increased, the current decreases.
And since P = VI = (current) squared × resistance,
higher voltage means less resistance losses during transmission.
That's why power transmission lines carry 100,000 volts
or more, but your house uses 120 volts. Power plant
voltage is "stepped up" to 100,000 volts,
sent hundreds of miles, then the 100,000 is "stepped
back down" to 120 volts before it reaches your
house.
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