- Electric current can act like a magnet: it attracts objects made of certain metals, such as iron. When electric current flows through a wire, it generates a magnetic field. Coiling the wire strengthens the magnetic force. This coil is called a solenoid. The magnetic field produced inside the solenoid is an electromagnet. The strength of this electromagnet increases when a core of magnetic material, such as iron, is placed inside the solenoid.
- Unlike the magnet that holds a piece of paper on a refrigerator, an electromagnet is a temporary magnet. It exerts a magnetic force only while electricity flows through it. Electricity is necessary to make electromagnets push or pull magnetic objects. When the circuit is closed, the flow of electricity stops and the electromagnet releases the object.
- We use electromagnets every day. Doorbells, speakers and electric motors are some common applications of electromagnets. Electromagnets are used to generate electricity in power plants and pick up cars at junk yards. Maglev trains use magnets to hover above the rails without wheels. These trains run very smoothly at speeds up to 300 miles per hour.
- We can control the magnetic energy of electromagnets by turning their magnetic fields on and off. For example, large electromagnets can attract large objects such as cars or turbines. When the current flowing to the electromagnet is turned off, the electromagnet can release the car or stop turning the turbine. If a doorbell contained a permanent magnet instead of an electromagnet, the bell would continue to ring even after you stopped pushing the button.
- Materials to make an electromagnet"Homopolar - 2.jpg" is Copyrighted by Flickr user: oskay (Windell Oskay) under the Creative Commons Attribution license.
You can make an electromagnet with insulated wire, an iron bolt or nail and a D-cell battery. First, wrap a tight, even coil of wire around the bolt. Leave a few inches of wire at each end of the bolt. Use wire strippers or sand paper to strip a half-inch of insulation from the ends of the wire. Attach one end of stripped wire to the positive terminal of the battery; attach the other end of wire to the negative terminal. Secure the connections with electrical tape or alligator clips. Try to pick up a small metal object such as a paper clip with the bolt. Disconnect the wires from the battery. You can increase the strength of the magnet by using a longer wire and wrapping more coils around the bolt or by connecting to a battery with greater voltage.
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