Department of Physics and Astronomy PHYS420: Physics Demonstration THIS IS SOMETHING WE SEE AND USE EVERYDAY! University of British Columbia Presenter: Eric Yeh
What are we doing today? • We are going to learn the basic functions, principles, and applications of an electric motor. • We are also going to build a very simple motor today right here in this classroom.
What is a Motor? • Definition: A rotating machine that converts electrical power (either alternating current or direct current) into mechanical power. Is this definition very satisfying?
The Types of Motor • DC (Direct Current) Motor • AC (Alternating Current) Motor • Linear Motor • Stepping Motor • Reluctance Motor • The type of motor that we are going to see today is a type of DC motor.
How Does A Motor Do Work? There are couple main principles behind a working DC Motor. In simple terms, they are: • Ampere’s Law • Right Hand Rule • The Magnetic Field & Force • Torque & Power
The Electromagnet • Electromagnets are usually in the form of iron core solenoids. • The iron nails line up with the smaller driving magnetic field produced by the current in the solenoid. • This multiplies the magnetic field by factors of tens to even thousands. • The solenoid field relationship is • k is the relative permeability of the iron, shows the magnifying effect of the iron core. μ0 is the permeability of the air.
The Motor that We are Building • Materials Required: • One 'D' Cell Alkaline Battery • 2 Pieces of Aluminum Tape • Two Large Paper Clips • One Rectangular Ceramic Magnet • Heavy Gauge Magnet Wire (the kind with red enamel insulation, not plastic coated) • Fine Sandpaper • Optional: Glue, Small Block of Wood for Base
Starting about 8 cm from the end of the wire, wrap it 7 times around the battery provided. Cut the wire, leaving a 8 cm tail opposite the original starting point. Wrap the two tails around the coil so that the coil is held together and the two tails extend perpendicular to the coil. On one tail, use fine sandpaper to completely remove the insulation from the wire. Leave about 0.5 cm of insulation on the end where the wire meets to coil. On the other tail, lay the coil down flat and lightly sand off the insulation from the top half of the wire only. Again, leave 0.5 cm of full insulation on the end and where the wire meets the coil. The Motor that We are Building
The Motor that We are Building • Bend the two paper clips into the following shape • Use the aluminum tape to hold the loop ends to the terminals of the "D" Cell battery • Stick the ceramic magnet on the side of the battery as shown:
The Motor that We are Building • Place the coil in the cradle formed by the right ends of the paper clips. • You may have to give it a gentle push to get it started, but it should begin to spin rapidly. • If it doesn't spin, check to make sure that all of the insulation has been removed from the wire ends.
What about a Generator • The current running through coils of wire would produce magnetic field that attracts or opposes the existing permanent magnet, which then drives the coil of wire to move or rotate. • Reversely, coils of wire moves or rotates in a magnetic field would also produce a current. This is what a generate does.
How can Motors and Generators help us? • With the theory of conservation of energy, we know that the energy will not disappear. Rather, energy would change from one form to another. In our discussion today, we have seen electrical energy turn into mechanical energy and also from mechanical to electrical. • Motors would help us to utilize the electrical energy that we have to do work through the form of mechanical energy. • Generator does the opposite. It transforms mechanical energy into electrical energy. • Generator is able to provide us with the source of electricity when we provide other forms of energy or materials that could react to release energy.
A Better Definition • Electric motors involve moving or rotating coils of wire which are driven by electric current producing magnetic force that opposes the magnetic field. They transform electrical energy into mechanical energy.