Force and motion
Force and Motion
Experiments with Batteries and Motors
This section shows two more experiments you can do with a DMM. * The first one answers the question, “Why do batteries come in different sizes?” By measuring the current coming from various batteries, you can see how different size batteries can supply different amounts of current.
- The second experiment explores what happens when a motor has things attached to its shaft. Because it is drawing more current, it will go dead much more quickly, the more it is trying to turn. There are two important Warnings attached to these experiments:
- **TO AVOID DAMAGE TO THE METER, USE THE 10 A. SETTING AND 10 A. JACK IN BOTH EXPERIMENTS. **
- **TO AVOID DRAINING THE BATTERY, MAKE THE MEASUREMENTS QUICKLY, AND DISCONNECT THE CIRUCITS WHEN YOU ARE DONE. **
Comparing batteries
This diagram shows how to test the current from a coin battery. To test any other kind of battery, use the same DMM settings and connections. Touch the red probe to the (+) side of the battery, and the black probe tio the (-) side.
What Happens when a Motor is Working Harder
The video above shows how to measure the current drawn by a motor under different conditions. For example, the motor might have nothing attached to its shaft, as in the first diagram below, it might have a wheel attached, as in the second diagram, or it might even have things attached to the wheel. What changes each time?
Measuring the current drawn by a motor
How much current does the same motor need when a wheel is attached to the shaft?
