ARBOR SCIENTIFIC P8-8300 World’s Simplest Motor Instruction Manual

: June 11, 2024
: ARBOR SCIENTIFIC

Table of Contents

Contents
Background
Activities
Related Products
References
Read User Manual Online (PDF format)
Download This Manual (PDF format)

ARBOR SCIENTIFIC P8-8300 World’s Simplest Motor

Background

Use the World’s Simplest Motor to study electricity and magnetism. Show energy conversions. Show how electricity creates magnetic fields and how it is used to create motion.

The discovery that currents produce magnetic fields was made by Hans Christian Ørsted in 1820. Ørsted made his discovery during a classroom demonstration on “electricity, galvanism, and magnetism.” Because Ørsted made his important discovery while teaching, the American Association of Physics Teachers awards a medal named after him each year to a teacher who has made a significant impact on the teaching of physics.

Figure 1 shows a modification of Ørsted’s experiment. A central wire carrying a strong current is surrounded by several compass needles. The dot signifies that the current on the wire is emerging from the page. If there is no current in the wire, then the compass needles would point toward the magnetic north pole of the earth. But when a strong current is present in the wire, the compass needles align themselves with the magnetic field created by the current. Adding more compasses suggests that the magnetic field is circular and surrounds the wire, as in Figure 1. This is what surprised Ørsted. Not only is the field perpendicular to the current, but it is circular!

Field lines are used to represent the magnetic field in Figure 2. The spacing between the lines represents the strength of the field—the denser the lines the stronger the field. Notice that the spacing of the lines increases with distance from the wire. This represents the 1/r decrease in the strength of the field—just like the decrease in the brightness of a candle.

Figure 3 is another representation, from a different angle, of the single wire carrying a current and the magnetic field that it creates. The Right-hand Rule can be used with a single wire to show the direction of the field lines or current.

What happens if you put a loop in the wire, as in Figure 4? If you follow the right-hand rule all the way around the loop, you’ll see that all of the magnetic field lines inside the loop point in the same direction and field outside the loop point in the same direction. Inside the loop, however, there is a high concentration of magnetic field lines that point in the same direction. Dense field lines indicate a high magnetic field. The quantitative description of the relationship between current and the magnetic field it creates is called Ampere’s Law and it states that the magnetic field is proportional to the current. Thus, one loop of wire, regardless of how big the wire is, will create roughly the same magnetic field as another wire, as long as the same size current runs through it. But, if there are multiple loops of wire, then each loop creates its own field and the magnetic field is very strong as compared to a single loop with the same size current.

wire are down against the metal supports and a current is flowing through the wire. The coil will want to align its magnetic field with the field from the magnet. If the coil always had current flowing through it, it would tend to get stuck in one position. When properly assembled, the motor will have current for half of a turn. It will turn to try to align itself. Then the motor coasts through the other half of the turn to allow it to keep going before it is charged again. Otherwise, it would want to spin back the other way.

Activities

Put compasses around the magnet. Turn the magnet and see the magnetic field created. Without the magnet, place the compasses near the coil of the motor. Slowly turn the coil and show how the magnetic field is created when current is flowing through the coil. Note the direction of the magnetic field.
Use a Magnaprobe to see the magnetic field surrounding the wire in three dimensions.
Flip the magnet over. How does this affect the performance of the motor?

Electromagnetic Force Demonstrator (P6-2625) The Electromagnetic Force Demonstrator is a dynamic way of showing the interaction between magnetism and electricity.
Homopolar Motor Kit (P8-8350) You’ve seen the World’s Simplest Motor™. We have a classroom set so you can make one that’s even simpler than that…
Lenz’s Law Apparatus (P8-8400) Experience the fundamental principle behind electric motors with this demonstration.

800-367-6695 | www.arborsci.com
©2023 Arbor Scientific All Rights Reserved