This project involves building one of the simplest types of electric motors, a homopolar motor. By creating a circuit with a battery, a magnet, and a conductive screw, you can demonstrate how electrical energy is converted into mechanical motion.
If an electric current is passed through a conductive screw in the presence of a magnetic field, then the screw will experience a rotational force (torque) due to the Lorentz force, causing it to spin and function as a simple motor.
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Place the head of the screw onto the center of the magnet.
Let the point of the screw hang down.
Hold the battery and touch the positive terminal to the head of the screw.
Now, take the copper wire and touch one end to the negative terminal of the battery.
Touch the other end of the wire to the side of the magnet.
Observe what happens to the screw and magnet.
Experiment with flipping the battery or the magnet to see how it affects the direction of the spin.
When the circuit is completed, the screw and magnet will begin to spin rapidly. This is because the current flowing from the battery, through the screw, and to the magnet creates a magnetic field that interacts with the field of the permanent magnet. This interaction produces a force (the Lorentz force) that creates a torque, causing the rotation.
The direction of the electric current and the orientation of the magnetic field.
The direction and speed of the motor's rotation.
The type of battery, magnet, and screw used.
The wire and battery can get hot, so be careful not to hold them for too long. Neodymium magnets are very strong and can pinch fingers or damage electronic devices. Keep them away from computers, phones, and credit cards.
Have your motor assembled and ready to demonstrate live.
Use clear diagrams to explain the flow of current and the direction of the magnetic fields and the resulting force.
Discuss the applications of electric motors in everyday life, from fans to electric cars.
The Lorentz force is the force exerted on a charged particle moving through a magnetic field. In this motor, the moving charges are the electrons in the electric current, and the force on them is what creates the torque that spins the motor.
It is called a homopolar motor because the polarity of the magnetic field and the direction of the current do not change as the motor rotates. This is different from most conventional DC motors, which use commutators to reverse the current direction.
You can experiment with different batteries and magnets, but a strong neodymium magnet and a fresh battery will give you the best results. The stronger the current and the magnetic field, the faster the motor will spin.
