Electromagnets

What is an Electromagnet?
Although the term “electromagnet” may sound overwhelming and complicated, electromagnetism is a relatively basic concept and easy to comprehend. An electromagnet is a type of magnet that produces its magnetic field by the flow of an electric current. When the current that fuels the electromagnet ceases, the electromagnet loses its magnetic traits. Jefferson Lab sums up how electromagnets work, stating “An electromagnet works because an electric current produces a magnetic field. The magnetic field produced by electric current forms circles around the electric current."
A Representation of how an Electromagnet Works
A Representation of how an Electromagnet Works


The Basic Design
A straightforward electromagnet can be made by wrapping a wire around an iron core. This wrapped wire is called a solenoid. The amount of current going through the solenoid determines how strong the electromagnet will be. You can increase the amount of current by increasing the length of the wire, tightly wrapping the solenoid around the magnet, and by using a powerful energy source to manipulate the current.
A Simple Electromagnet
A Simple Electromagnet


The Right Hand Rules
Now you may be wondering how to determine in which direction the magnetic field actually points. Luckily British Physicist John Ambrose Fleming discovered a handy trick (see what we did there?) in order to pinpoint the direction of the magnetic field.
1. The thumb indicates the direction of the electric current.
2. The fingers of the right hand are curled to match the curvature and direction of the motion and magnetic field. The thumb indicates the direction of the electric current.
A Visual Representation of the 1st Right Hand Rule
A Visual Representation of the 1st Right Hand Rule

The second right hand rule is used to determine the magnetic force, current, and the magnetic field. If you are given any two out of the three factors, you can easily determine the third by using this simple rule
1. Point your index finger in the direction of the current.
2. Point your middle finger in the direction of the magnetic field
3. Your thumb now points in the direction of the force!
A Visual Representation of the 2nd Right Hand Rule
A Visual Representation of the 2nd Right Hand Rule

If you are still confused with these rules, these videos should help!





Electromagnets in the Real World
Now that you have a basic understanding of the rudiments of electromagnets, you’re probably curious as to their role in the real world. Electromagnets are used in a variety of products, and machines. Some common uses include magnetic locks, generators, and electric bells. The two products that we are going to focus on in this e-book are motors and speakers.
Motors
An electromagnet is the foundation of an electric motor. The premise of an electric motor is that it uses electrical energy to catalyze the physical movement, mechanical energy. Such motors may be powered by either a direct or alternating current (which were invented by Edison and Tesla respectively) although the ones we created in class were direct current, from a standard 9 volt battery. Traditionally, after the “half-turn” of motion that occurs in an electric motor, the motor creates a complete rotation by flipping the field of the electromagnet. This flip causes another “half-turn” of motion, a process that repeats many times. The flip occurs by changing the direction of the electrons flowing in the wire and the physical repercussion is the movement of the motor.

Speakers
Like motors, speakers use magnets to function. Speakers contain electromagnets (called voice coils) to translate electric signals to audible sound. Inside a speaker, an electromagnet is placed in front of a permanent magnet. Through alternating current, a magnetic field is created around the coil. As current passes though the electromagnet, the direction of its magnetic field constantly changes. The electromagnet is attached to a cone to pump the sound waves.

Depending on the type of speaker (headphones vs. boom-box, etc.) direct current may be utilized with the use of an amplifier, but we did not incorporate such a device in our in-class experimentation.

Conclusion
Electromagnets. At first a daunting word, this concept is really rather simple. The magnet gets its charge from the current of electricity. This concept is used in hundreds of different ways- ranging from motors, to hard drives, to wrist watches and speakers. Electromagnets are used in nearly every appliance we use, and although it may not be duct tape, the principles of electromagnetism apply to many practical situations.

Here are Some Great Links to Further your Knowledge in Electromagnets
http://www.britannica.com/EBchecked/topic/183324/electromagnetism
http://siarchives.si.edu/history/jhp/joseph21.htm
http://www.magnet.fsu.edu/

Sources
http://education.jlab.org/qa/electromagnet_is.html
http://www.coolmagnetman.com/magelect.htm
http://physics.kenyon.edu/EarlyApparatus/Electricity/Electromagnet/Electromagnet.html
http://education.yahoo.com/reference/encyclopedia/entry/electromg
http://www.encyclopedia.com/topic/electromagnet.aspx