Data Sheet
Project 12
Motor Resistance
Build the circuit, set the meter (M5) to the 1A
setting, and turn on the slide switch (S1). The
motor (M1) spins and the meter measures the
current. Do this with and without the fan on the
motor.
Calculate the resistance of the motor,
with and without the fan. How does
your calculation of the motor’s resist-
ance compare with its typical resist-
ance? What factors could have
caused the difference?
Calculate the power of the motor, with
and without the fan. Does the motor
use more power when the fan is on
it? Why?
The battery voltage is 4.5V, so use your current
measurements to determine the motor resistance
using Ohm’s Law.
The motor resistance is typically 5-20 ohms with
the fan and 25-100 ohms without the fan.
Note: Your actual results may vary. Your M5
meter is a simple meter; don’t expect it to be as
accurate as normal electronic test instruments.
Calculate the power of the motor using: Power =
Voltage x Current.
Voltage
Current
Resistance =
!
WARNING: Moving parts. Do not
touch the fan during operation.
!
WARNING:
Do not lean over the motor.
1A
Project 13
1A
Build the circuit, set the meter (M5) to the 1A
setting, and turn on the slide switch (S1). The
meter measures the current through the elec-
tromagnet. Drop the thin rod into the electro-
magnet; it will be suspended in mid-air.
Use Ohm’s Law to calculate the resistance
of the electromagnet’s resistance, and com-
pare with its typical resistance.
The electromagnet is just a large coil of wire, its
resistance is about 30 ohms.
Wires can generally be as long as desired with-
out affecting performance, just as using garden
hoses of different lengths has little effect on the
water pressure as you water your garden. How-
ever there are cases where the length and size
of a pipe does matter, such as in the water lines
for your city. Similarly, wire length and size are
important for electric power lines transporting
electricity from a power plant in a remote area
to a city.
Electromagnet Resistance
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