Elenco Green Projects - Manual (Page 26)

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Project #23
Water Wheel
Remove the wind fan from the motor shaft and
replace it with the water wheel. Watch how the
current is different with the larger water wheel.
The water wheel is heavier, so it takes more
current to spin it, and doesn’t get as fast. Try laying
something on the water wheel to give it even more
weight.
Project #25 Motor Voltage
Modify the preceding circuit into this one. Set the meter
(M6) to the 5V setting and place the wind fan on the motor
(M4). Push and release the press switch (S2) and watch
the voltage on the meter as the motor speeds up and
slows down.
Without pressing the switch, spin the fan clockwise with
your finger and watch the voltage. In the preceding
project, the current dropped as the fan sped up - now you
see why. The spinning fan produces a voltage in the
motor; this voltage opposes the voltage from the battery,
reducing the current as the motor speeds up.
How will the voltage and current change if you replace
the wind fan with the water wheel? Try it.
Project #24 Motor
How does electricity turn the shaft in the motor? The answer is
magnetism. Electricity is closely related to magnetism, and an
electric current flowing in a wire has a magnetic field similar to
that of a very, very tiny magnet. Inside the motor is a coil of wire
with many loops. If a large electric current flows through the loops,
the magnetic effects become concentrated enough to move the
coil. The motor has a magnet inside, so as the electricity moves
the coil to align it with the permanent magnet, the shaft spins.
Build the circuit shown. Set
the meter (M6) to the
50mA setting and place
the wind fan on the motor
(M4). Push the press
switch (S2) and watch the
current on the meter as the
motor speeds up.
Do you know why the
current drops as the fan
speeds up?
50mA
5V
Electricity is generated
when you spin the motor
shaft. A coil of wire is on
the shaft, and as it spins
past the permanent
magnet an electric
current is created in the
wire.
See projects 1 & 3 if you need to
recharge the battery (B4).