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You may be familiar with permanent magnets—the kind that hang on a refrigerator. But did you know that other magnets, called electromagnets, can be turned on and off? When turned on, electromagnets act just like permanent magnets, but if you turn them off, their magnetic properties disappear. Electromagnets are an important part of many electronic devices, like motors, loudspeakers, and hard drives. You can create an electromagnet with a simple coil of wire and a battery. In this project, you will explore whether the strength of an electromagnet changes with the number of turns in the magnet's coil. You will measure the magnet's strength by counting the number of paper clips your electromagnet can lift.


AREAS OF SCIENCE
Electricity & Electronics
In this science project, you will make an electromagnet by wrapping a coil of wire around an iron core. You will then investigate whether the number of coils changes the electromagnet's strength.
Electromagnets, or magnets that use the magnetic field created by electrical current flowing through a wire, lie at the heart of many electrical devices, ranging from simple things like doorbells to complex machines like particle accelerators. The strength of electromagnets varies, but some electromagnets are strong enough to lift entire trains! So how does an electromagnet work? How does electric current—the movement of electric charges—make a magnet?

When electric current flows through a wire, it creates a magnetic field. You can prove this to yourself with a magnetic compass (see the Science Buddies Abbreviated Project Idea Using a Magnet as an Electrical Current Detector, and the Electricity, Magnetism, & Electromagnetism Tutorial to learn more). The magnetic field around a straight wire is not very strong. But if the wire is wrapped in a coil, the fields produced in each turn of the coil add up to create a stronger magnetic field. When the coil is wrapped in the shape of a cylinder, it is called a solenoid. When electric current flows through the solenoid, it creates a magnetic field very similar to that of a bar magnet (Figure 1).



solenoid-magnetic-field

Figure 1. Illustration of a solenoid and the magnetic field created by the flow of current. Note that if the current changes direction, so does the magnetic field.

If an electromagnet consists only of coiled wire (if it has nothing but air in its middle) then the magnet will not be very strong. But if you place a piece of iron in the middle of the coil—an iron bolt, for example—then the piece of iron, called the core of the electromagnet, will make the magnetic field much stronger. This is because iron is ferromagnetic. It contains lots of tiny areas, called magnetic domains, that act like small magnets. As soon as the iron core is placed in the coil, the magnetic domains line up with the magnetic field made by the solenoid. As a result, the strength of the magnetic field greatly increases.

In this project, you will investigate how the strength of the magnetic field produced by an electromagnet changes as the number of turns in the coil increases.

To do this project, you should do research that enables you to understand the following terms and concepts:

  • Electromagnet
  • Electric current
  • Solenoid
  • Core
  • Ferromagnetic
  • Magnetic domains
  • How does an electromagnet work?
  • Why does an electromagnet have magnetic properties only when energized?
  • Does increasing the current flowing through a coil of wire increase or decrease the strength of the magnetic field?
  • What does adding an iron core to an electromagnet do to the magnetic field created by the electromagnet?