Students these days like things that move. Parents like to see their students be engaged. That’s why when I have the chance to teach about magnets I’ll eventually get around to discuss direct current (DC) motors.
DC motors have some unique qualities that can be used to teach basic principles of electromagnetism. Most students understand how to make an electromagnet using a battery, wire and a nail. It can be difficult to understand the movement of electrons in the wire that are used to create an electromagnetic field (emf). However, it is undeniable that something happens when the electromagnet picks up a paper clip. That simple process demonstrates the attracting qualities of an electromagnet.
In a similar fashion the wire windings around the armature assembly are attracted to and repelled from the fixed magnets. Once this process is understood, the next principle is the idea of a “switch.” In this case, this assembly is called a commutator and it is involved in the process called commutation. The commutator takes care of acting like a switch and is used to help reverse the polarity of the circuit when the electricity flows through it.
In the final analysis, DC motors have three basic principles:
- attraction and repulsion,
- a switch (commutator), and
- reversing the polarity of a circuit.
When the DC motor is wired correctly and these three principles work together, the DC motor will hum merrily along. This is what caused me to be enthralled about building my first DC motor. Finding the materials, following the directions, wiring the fixed magnet, wiring the armature, and adjusting the commutator. This is one of the reasons I feel it is important for those students that have a preference for Science, Technology, Engineering, and Math (STEM) to have experience designing and building DC motors.
Quote for the Day: “Man’s mind, once stretched by a new idea, never regains its original dimensions.” — Oliver Wendell Holmes