Magnets on the Move
Warning!
Adult supervision: choking hazards
Please read the procedure before beginning! After reading, please watch the video. Some activities require more time and cleanup than others. You also have the choice of performing these activities in a way that suits your needs.
Materials
Homopolar Motor
· AA Battery
· 4 neodymium magnets
· Copper wire
Water Compass
· Large t-pin
· Cork
· Paper Cup
· N/E/S/W Stickers
· Water (not included)
Compass (not included)
Frog Ring Game
· 4 ring magnets
· Straw
· Clay
· Paper cup
· Frog Stickers
· Crayons
· Scissors
Procedure
Homopolar Motor
1. Stack the neodymium (silver) magnets so that they stick together.
2. Place the AA battery on top of the stack with the positive (+) terminal facing upward.
3. Bend one of the pieces of copper wire into a heart shape. Balance the middle of the heart on top of the positive terminal of the battery. The bottom part of the wire should be touching the neodymium magnets that are below the battery. The motor should start spinning (i.e. the copper wire will spin if it is balanced).
4. Experiment with other shapes of wire—the only requirement is that part of the wire must be touching the positive terminal of the battery, and part of the wire must be touching the magnets. Can you make an L shape? A spiral? What other shapes can you make? Does anything change if you flip the magnets?
Water Compass
1. Using one of the neodymium magnets from the homopolar motor, stroke down the length of one half of the t-pin 50 times. Be sure to use the same side of the magnet for the duration of this step.
2. Using the other side of the neodymium magnet, stroke down the length of the other half of the t-pin 50 times. Steps 1 and 2 will magnetize the t-pin.
3. Carefully press the t-pin through the center of the cork with the cork oriented horizontally (i.e. press through the cylindrical/curved part of the cork).
4. Fill the cup completely with water. Gently place the cork in the water with the t-pin horizontal, and it will turn so that one end of the t-pin points North and the other end points South.
5. To determine which end is North and which end is South, a compass can be used. Alternatively, in a location where the Sun is visible, it can be noted that the Sun rises in the East and sets in the West. Using this knowledge, determine which direction is East. North is to the left of East and South is to the right.
6. Place the stickers on the cup to determine the cardinal directions that were determined in step 5. The water compass is complete!
Frog Ring Game
1. Cut the straw to approximately 2.5 inches. This length can be measured using a ruler (such as the one on the STEM SAK bundle box), or it can be approximated.
2. The magnetic rings will be the ‘frogs.’ Use the frog stickers to decorate them.
3. Mold the clay into a base and secure it to the desk or table.
4. The magnetic rings will be the ‘frogs.’ Use the frog stickers to decorate them.
5. Mold the clay into a base and secure it to the desk or table.
6. Secure one end of the straw in the clay. This is where the frogs will ‘jump’ from!
7. Decorate the paper cup using the crayons—this will be the pond that the frogs will jump into!
8. Slide the magnet rings onto the straw. Do they stick together? What happens if you flip them over?
9. When the magnets don’t stick together, they repel one another– if you hold one of the rings down and release it, it will ‘hop’ off of the straw. The goal of the game is to make the frogs hop into the pond. Try moving the cup closer or farther away from the straw, or change the direction by changing the angle of the straw. Experiment with different lengths of straw.
Science Behind it!
Magnets have many interesting properties! Magnetism is caused by the motion of tiny electric charges that you can’t see or feel. Each magnet has a positive and negative side. Two magnets will attract one another if the positive side of one is facing the negative side of the other. They will repel one another if the positive side of one is facing the positive side of the other, or if the negative side of one is facing the negative side of the other.
Homopolar Motor
The homopolar motor creates electric charges in the copper wire as it conducts electricity from the battery in a circuit that includes the magnets. These charges interact with magnetic charges in the magnets, which causes the motor to spin! If the magnets are flipped over, the motor spins in the opposite direction since the opposite side of the magnet is making contact with the battery.
Water Compass
The water compass works because Earth is magnetic! Earth has a relatively weak magnetic field that is strongest near the poles. When the t-pin is magnetized and allowed to float freely in water, it will turn in response to Earth’s magnetic field so that one end always points North.
Frog Ring Game
The frog game utilizes the fact that like charges repel one another. This is why the magnets have to be flipped a certain way for the game to work (if they are flipped the other way, the magnets attract and stick together).