An electromagnetic crane is a crane that makes use of the link between electricity and magnetism to produce the force required to lift heavy objects. The link between electricity and magnetism is a great topic for science projects, and even if a full electric crane project is a bit too hands-on for you, you can test the principles underlying it with a simpler electromagnet experiment. Whatever approach you want to take for the project, it will be a clear demonstration that moving charges generate magnetic fields, one of the key principles of electromagnetism.
Principles of Electromagnetism: The Motor Effect
The principle that allows an electromagnetic crane to work is that a moving electric charge generates a magnetic field. You can demonstrate this easily with a magnet and a simple electrical circuit in this experiment from the Exploratorium. Get between two and four small disc magnets (although other magnets will also work), 2 to 3 ft (60 centimeters to 1 meter) of wire and one or two 1.5 V batteries. The aim is to connect up the circuit with the wire dangling off the side of a table or other raised surface. Attach the battery (or two batteries connected in series) to the table with masking tape, near the edge, and tape the two ends of the wire to the table near the battery (so the ends can reach the free battery terminals). The remainder of the wire should dangle down over the edge of the table.
Connect the two ends of wire to the terminals of the battery. A current will begin to flow in the wire. Now connect your magnets together as a cylinder and bring them close to the wire. The wire will move as you bring the magnet close to it. This is because the current flowing through the wire generates a magnetic field, which interacts with the magnet.
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Basic Electromagnet Experiment: Strength of Electromagnets
If you want more of an experiment but don’t want to make a complete electromagnetic crane, a simple demonstration, with this experiment from Study.com, can reveal which factors affect the strength of an electromagnet. Get two (or more) batteries, some electric wire, a nail (at least 3 inches long is ideal) and several paperclips. You can make a basic electromagnet by wrapping the wire around the nail like a coil, and then attaching both ends of the wire to the terminals of the battery. However, a scientist wouldn’t be satisfied with such a simple demonstration. How strong is the magnet? And what would affect how strong the magnet is?
Create a basic electromagnet with a set number of wraps of wire around the nail, say 15. Use one battery for this first test. Now connect the wire to get the electromagnet working, and see how many paperclips it can lift up. Note down the maximum number of paperclips, the number of wraps used and the number of batteries used. Now try the test again but increase the number of wraps, to 30, for example. How many paperclips can the setup lift now? Note the result down. Now try adding another battery in series with the first, to increase the voltage powering the circuit. Can it lift more paperclips than it could with a single battery, for a given number of wraps?
Making an Electromagnetic Crane
An electric crane project is a natural continuation of the projects covered so far. The basic principle that a moving charge generates a magnetic field explains why it happens, and you can use this to make an electromagnet by wrapping a current-carrying wire around a metallic core. In addition, you’ve found that a greater voltage or more wraps of wire increases the strength of the magnet.
Use these results to create your own electromagnetic crane. The actual construction of your crane can vary, but the key elements are a pulley system with the electromagnet attached to the end and a stable base for your crane (see Resources for an example). You can replicate the experiment from the previous section with your crane, or alternatively, use what you learned to make a more powerful crane.