Elenco Green Projects - Manual (Page 68)

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Project #110 Energy Transmission Loss
Saving Energy
Build the circuit shown. Set the meter to the
50mA setting. Set the slide switch (S5) to
position C. The battery operates the radio,
horn, red LED, and motor, just like batteries
operate stuff in your home. The meter shows
how much current is used to operate them;
the more current is used, the faster the
battery will run out.
You can make the battery last longer if you
turn off some things. Remove the radio, horn,
LED, or motor from the circuit, and see how
much the current drops. Then remove
another. Some devices use more current
than others, so it helps most if you
disconnect the highest current device - find
out which one it is.
Push the press switch (S2); the
motor (M4) spins the fan, the
red LED (D1) lights, and the
meter (M6) measures the
voltage across them.
If the slide switch (S5) is in
position B, the electric current
takes the short path to the
meter/LED/motor. If the slide
switch is in position C, the
current takes the longer path,
and the voltage available at the
meter/LED/motor is lower due
to more resistance in the path.
Remove the LED or motor and
see how the voltage changes.
If less current is used, less
voltage will be lost along the
way.
Project #109
Reducing how much
energy we use is just
as important as finding
new sources of clean
energy.
Electrical wires have low resistance, but
when you are transporting large amounts of
electricity over large distances (such as
between power plants and cities), even low
resistance causes large power losses. In
this circuit a resistor in the pivot stand
simulates having a very long wire.
When electric power companies transport
electricity long distances (like between
power generating plants and cities), they
use high voltages and low currents since
this reduces power loss in the wires.
Transformers convert this to 120V, which is
supplied to homes and offices.
50mA
5V
See projects 1 & 3 if you need to recharge the battery (B4).