Data Sheet

-41-
51. Ohms
Build the circuit and you will see the heart LED (69) and lamp (76) will
light and the motor (95) spin at the same time. Because the lamp (76)
and motor (95) are in parallel with the heart LED (69), the internal
resistance of the heart LED (69) does not signicantly limit the current
path through the lamp (76) and motor (95).
Recall from project #28 that Ohm’s law stated V=I*R. Solving for R
yields R=V/I. This shows that 1 Ohm represents the resistance in a
circuit that produces 1 Amp of current when subjected to a potential
difference of 1 Volt.
52. Conductivity Tester
Build the circuit shown on the left. Try connecting various objects
across points A and B (they will have to be small objects that can touch
the pins at points A and B like a paper clip). If the object is a very good
conductor, then it will enable all the current to ow through it and the
lamp (76) will light. If the object is a very poor conductor, then very little
current will ow through it and the lamp (76) will not light.
This conductivity tester is similar to the one in project #33 but here the
light coming on means a good conductor, while in project #33 the light
coming on meant a poor conductor.
WARNING: Moving parts. Do not
touch the motor during operation. Do
not lean over the motor.
!
1st level