Electromagnet: Exact Definition
An electromagnet produces a magnetic field when an electrical current flows through conductive wires (like copper) that are wrapped around a core (a metal rod) that can accept a magnetic field.
While a permanent magnet has a magnetic field encompassing the magnet at all times, an electromagnet has a magnetic field that s present only when an electrical current passes through it. You can turn an electromagnet on or off.
What Is a Magnet: Complete Explanation
With this in mind, a magnet, also known as a permanent magnet, always creates a magnetic field. For example, a permanent magnet is created from ferromagnetic materials (iron, cobalt, or nickel).
The atomic structure of atoms in a ferromagnetic material is lined in and aimed in the same direction. Additionally, the orientation of ferromagnetic materials allows them to be magnetized.
Atoms grouped will form their own magnetic domain, a positive or negative magnetic domain. However, the magnetic domain is random. In the image below on the left ( unmagnetized material ), you can see the randomized direction of the domains.
Unmagnetized materials can be magnetized. The most common form of creating magnets is the process of powder metallurgy (PM).
- Elements are ground into fine powder.
- The powder is heated and compressed inside a form. The form comes in any desired shape. A U shape, a flat box shape you name it.
- A magnetic field (aligning field) is applied during the heating and compaction phase the aligning field readies the magnet to accept a magnetic charge.
- The process is completed when the newly formed magnet (lacking any magnetic properties) is subjected to magnetic forces. The newly formed almost magnet is placed close to a much larger magnet. The electrons located in the almost magnets atoms will orient themselves to match their spins to the magnetic field of the larger magnet.
- The almost magnet is now a permanent magnet. A reasonable expectation of the permanent magnet is that it will lose approximately one percent of its magnetic field each year. If you take care of your magnet, it will last a long time. We ll talk about caring for your magnets a bit later.
What Is an Electromagnet: Complete Explanation
An electromagnet is a magnet that produces an invisible magnetic field of varying strength based on the electricity flowing through it. While a permanent magnet always has a magnetic field, an electromagnet only has a magnetic field when an electrical current is passing through it.
A permanent magnet has a constantmagnetic field, but electromagnets cease having a magnetic field when the electrical current stops. The ability to control the magnetic field, and increase or decrease its intensity, has made the electromagnet incredibly popular and widely utilized in common everyday electronics.
How Does an Electromagnet Work?
An electromagnet is a piece of metal (think of it as a core) that s wrapped (around and around) with a long strand of conductive wire (generally copper). When you introduce an electrical current (turning on a switch), current flows throughout the wire.
The current flowing through the coiled conductive wire creates a magnetic field. The magnetic field magnetizes the metal core. The metal core now behaves like a permanent magnet. When the electricity turns off, the core is no longer magnetic.
In the image above, the battery represents the electrical current. The current flows into the coil of wires at one end, the south, and exits the battery at the other end of the coil, the north. The north and south ends of the diagram also represent the opposite forces of the magnetic field, the North and South.
Electromagnets are also known as temporary magnets. Temporary magnets lose their magnetic charge when you remove the electrical current.
We d be completely remiss in our discussion of electromagnets not to tell you how you build your own electromagnet! Let s build an electromagnet; it s easier than you might think.
How Do You Create an Electromagnet?
While it sounds daunting, it s quite simple to create an electromagnet.
- Step 1: Find some copper wire; we suggest around 12 AWG.
- Step 2: Locate an iron nail, maybe three or four inches. A longer nail is better than a shorter nail!
- Step 3: Wrap the copper wire around the nail. Don t overlap the wire on top of itself.
- Step 4: Strip the ends of the copper wire and remove the insulation. About an inch of bare wire on each end of the coil is perfect.
- Step 5: Attach one of the copper wires to the positive end of the battery. Attach the other end of the copper wire to the negative end of the battery.
- In the diagram above, the construction shows alligator clips. This is a bit of overkill. You can use electrical tape or your fingers to make a connection. (This isn t rocket science!)
- Step 6: The iron nail becomes magnetized with the current flowing from your battery through the copper wires. Try it out with some paperclips or staples.
- Step 7: The wire will heat up as the current passes through it. Mind your fingers, and don t try to brand your pet.
There you go! With minimal tools and hardware, you, too, can create an electromagnet. It s hard to imagine, but there was a time not so long ago when electromagnets hadn t been invented. Who invented them?
Who Created the Electromagnet?
In 1825, British electrical engineer William Sturgeon invented the electromagnet. Sturgeon built the electromagnet from a horseshoe-shaped piece of iron, wrapping the iron with wire.
When current passed through the wire, the horseshoe became magnetized. Sturgeon proved that the magnetic field increased in strength when higher levels of current passed through the wire coils. He lifted a nine-pound weight through a seven-ounce electromagnet core wrapped with wire.
In 1830, American inventor Joseph Henry demonstrated the use of the electromagnet by sending an electrical current through a wire stretched out for one mile, activating another electromagnet on the other end of the wire.
The electromagnet on the far end of the wire (one mile away) started a bell to ring. Thus began the age of the telegraph.
What Are the Applications of Electromagnets?
Electromagnetic technology has advanced tremendously since its invention in 1825, yet its principles remain the same today. Electromagnets are (literally) everywhere around us.
We ll bet that by the time you ve finished reading this article, you ll be able to locate ten or fifteen electromagnetic applications within ten feet of where you re sitting right now!
Examples of Electromagnets In the Real World
Today, you ll have a hard time not finding electromagnets in use all around you. Let s start assembling a list!
Headphones and Speakers
Did you know that headphones and speakers have electromagnets in them? For example, how many headphones and speakers (don t forget yourcell phone!) are within your current line of sight? (We count twelve from our desk!)
Ahard diskdrive (HDD) contains a read-and-write head that magnetizes portions of the disk (called sectors). Each section has a one or a zero value assigned.
In addition, the hard disk has rotating platters (they look like CDs) that spin at high speed. As a result, the same read-and-write disk reads the magnetized sectors of the disk.
You don t need to look further than your front door to find an electromagnetic lock. Rapidly gaining popularity, electromagnetic door locks use electrical current to activate a door lock.
An electrical current is applied to the door lock, and the lock is activated (locked). No sooner than the electrical current is removed from the door lock, the lock is deactivated (unlocked).
Looking around your home, you ll be hard-pressed not to find avacuum, refrigerator,blender, washing machine, hair dryer, dishwasher, or microwave. But did you realize that each application also uses an electromagnet?
Automotive junkyards use electromagnets to lift cars and move them around the scrap yard. Electromagnets are also common items on construction sites, used to pick up and transport steel plates or scrap metals.
Magnetic Resonance Imaging
Electromagnets are common pieces in magnetic resonance imaging (MRI). Patients lie within a strong magnetic field for testing. First, the magnetic field stimulates the patient s protons. Then, the protons start to spin out of whack (equilibrium).
Accordingly, the protons realign when you deactivate the magnetic field. The MRI device allows physicians to differentiate between different types of soft tissue. The MRI will help identify aneurysms, strokes, blood clots, and inflammation (to name a few)!
Scanning Electron Microscopes
Electromagnets play a key role in scanning electron microscopes. As a result, scanning electron microscopes (SEMs) collect electrons (instead of light) to create a magnified image. Then, a series of electromagnets come together as a lens to focus the electrons on a collector.
Find scanning electron microscopes are used daily in science, medicine, manufacturing, and education. In the image above, a SEM collected an astounding close-up image of a fly s eye. Electromagnets helped to focus the image.