Q: My coils are not spinning. What's wrong?
A: If you are sure your battery is working, and your set-up matches the diagram shown for in the Project Idea, the following information provided from one of our Expert volunteers may help you troubleshoot:
- The removal of the insulation on only half of the wire on each end is critical. It must also be symmetric, that is identical on both leads. The diagram actually shows it pretty well. When you are looking at bare copper on one side, you should be seeing the bare copper on the other side. The motor depends on this to 'commutate' the current to the motor. That means it alternately turns the coil on and off once in every revolution. If all the insulation was removed on the leads, the coil would always be 'on' and just align to the magnet and not move.
- Try to balance the coil as carefully as possible so that it will spin easily and not have a 'heavy spot' somewhere in it's rotation. That will assure the best rotation and speed.
- The position of the magnet is critical because the magnetic field generated by the coil when it is energized must by synchronized to the position of the magnet. I found that in my first attempt with the magnet directly under the coil I would get attraction, but no rotation. When I changed the position of the magnet to the side (about 30 degrees) the motor started to spin. Also, place the magnet as close to the coil as you can without touching it.
Q: How come my voltage measurements across the axle supports always remain the same (stay at the voltage of my battery)?
A: The measurements definitely should be different. A possible problem might be that the coil axles are not in strong, constant contact with the axle supports. Check to make sure that your axles have not lost contact with their supports. A loss of the axle-support contact would lead to a constant voltage measurement that is equivalent to the battery voltage because you would have an open circuit. With an open circuit, measuring across the axle supports is equivalent to measuring the battery directly.
Another step to take is to try the measurements again. Monitor your meter very carefully to detect small changes in the voltage and try setting the meter so that you can see fractional changes in the voltage.
Q: I still don't see a change, what else can I do?
A: One idea is to remove the rotor from the supports and to read the voltage. One person can watch the meter while another person can put the rotor back on the supports. You can then look for a small voltage drop once you get the rotor back on and it begins to run again.
Q: What if I need help using a voltmeter?
A: There are many online resources that you can refer to if you need some extra help with using a voltmeter. For instance, here is one resource that gives instructions on how to use a voltmeter: http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Measurements/MeasVolt.html
Q: How can I learn more about using a multimeter?
A: If you are trying one of the variations that involves a multimeter, check out our Electronics Primer on using a multimeter:
http://www.sciencebuddies.org/science-f ... l?from=AAE
Q: Do the number of coils affect my voltage reading?
A: Yes, a greater number of coils should mean a lower voltage reading.
Q: How much of a voltage drop should I expect?
A: More current that flows through the battery and motor should mean more of a voltage drop. The exact voltage drop will vary among different individuals, but it will depend on the freshness of your battery and other details of how you've constructed your motor.
Q: Should fewer coils mean a faster rotation?
A: No. More turns will create a stronger magnetic field, which leads to a faster rate of rotation.
Q: What happens when the number of coils increases? Does this lead to more resistance?
A: Yes, more coils leads to increased resistance of electromagnets such as the rotor. You can read up on the magnetic fields of electromagnets to find out why. However, keep in mind that if you change any electric motor mechanically (or electrically), you will be affecting multiple variables. Keep in mind that good science experiments try to control for as many variables as possible so that when you measure an effect, you are measuring the effect produced from one variable at a time. For instance, when you change the number of coils with fixed voltage, same gauge wire, and same diameter, there are at least three variables affected, including the rotor mass and current through the coils.
Q: What should it look like?
A: A photo of the set-up for this project can be viewed here:
To see the working motor in action, check this short video created by one of our Ask an Expert volunteers: http://www.youtube.com/watch?v=5T5Nfi6N96Q
There are many threads at Ask an Expert that contain additional questions and answers related to this Project Idea. One thread you may find helpful is this one:
If you have other questions about the procedure or need assistance troubleshooting your project or the Experimental Procedure, please post your question in the forum for this kit at Ask an Expert: http://www.sciencebuddies.org/science-fair-projects/phpBB3/viewforum.php?f=59. Our team of volunteer Experts is available to assist. We attempt to reply to questions within 24 hours. Please note that you will need a free Ask an Expert account in order to post questions.