24
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.
See project 3 if you need to recharge the battery (
B4
).
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?
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.
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.
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.
PROJECT 26
• Motor Voltage
PROJECT 25
• Water Wheel
PROJECT 24
• Motor
5V
50mA