Electromagnets

1. Electromagnets What is an electromagnet? How does it work? Where are they used?

2. Electromagnets • An electromagnet is simply made of a wire and battery. • An electromagnet is produced any time current is flowing through a wire. • The current in the wire creates a magnetic field.

3. Fields Around a Wire • The field around a wire is circular and gets weaker as you get further from the wire.

4. What happens with a compass? • If you bring a compass near a current carrying wire, it will deflect (turn). The direction it turns depends on the direction of the current.

5. Fields Continued…. • Because the magnetic field around a wire is circular and perpendicular to the wire, an easy way to amplify the wire's magnetic field is to coil the wire, as shown in the picture. • The more loops you make the stronger the magnetic field becomes.

6. A magnetic nail • For example, if you wrap your wire around a nail 10 times, connect the wire to the battery and bring one end of the nail near the compass, you will find that it has a large effect on the compass. In fact, the nail behaves just like a bar magnet. • The more times you loop the wire, the stronger the magnet becomes. This is why you were able to pick up paper clips with this experiment in the lab.

7. Uses for Electromagnets: Maglev Trains • Maglev is short for magnetic levitation, which means that these trains will float over a guideway using the basic principles of magnets to replace the old steel wheel and track trains. • The first maglev train made its debut in Shanghai, China in 2003.

8. More on Maglev Trains • The big difference between a maglev train and a conventional train is that maglev trains do not have an engine -- at least not the kind of engine used to pull typical train cars along steel tracks. The engine for maglev trains is rather inconspicuous. Instead of using fossil fuels, the magnetic field created by the electrified coils in the guideway walls and the track combine to propel the train.

9. Maglev Trains • The magnetized coil running along the track, called a guideway, repels the large magnets on the train's undercarriage, allowing the train to levitate between 0.39 and 3.93 inches (1 to 10 cm) above the guideway. Once the train is levitated, power is supplied to the coils within the guideway walls to create a unique system of magnetic fields that pull and push the train along the guideway. The electric current supplied to the coils in the guideway walls is constantly alternating to change the polarity of the magnetized coils.

10. Maglev Trains in the U.S. • Plans have been in the works to build a Maglev Train from LA to Pittsburgh, but the cost is very high, so they have not started construction. • A prototype train is being built in Georgia by the American Maglev Company.

11. What else can Electromagnets do? • Make a speaker or microphone work. • They are used in read/write drives on your computer. • They are used in anything with an electric motor or solenoids. • Refrigerators, washer/dryers, vacuum cleaners, electric drills (and other tools), hairdryer, your car (windows, locks, seats), most toys that move, your garage door opener and much more!

12. Right Hand Rule • When you are designing a product that uses an electromagnet, it is important to understand the direction of the magnetic force, current and magnetic field. • 1st Right-hand rule: straight wire: • Thumb is current, fingers are the direction of the magnetic field.

13. 1st Right Hand Rule • Grasp the wire with your right hand. • Your thumb is the current, your fingers are the magnetic field (B). • The field will either point clockwise or counter-clockwise

14. 2nd Right Hand Rule • Your thumb is the magnetic force. • Your out-stretched pointer finger is the current. • Your middle finger is the magnetic field (B). I

15. An Example of the 2nd Right-Hand Rule • The current is going “up” the wire. Point your index finger up. • The magnetic field (in this case) goes into the page. • Which direction does the force go? • The force will be to the left!