How to Define Eddy Current
Eddy currents are small swirls of magnetic forces induced in conductive plates. Observe a flowing river or large stream. As the water flows downstream you may see small swirls on the water's surface that may appear to be spinning in different directions. These swirls are much like eddy currents. In electrical applications these swirls of magnet forces will also swirl in different directions. Certain machines take advantage of eddy currents for slowing large, rotating objects such as motors. Other machines use these induced currents to remove unwanted metal objects for sorting recycled products.
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Instructions
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Electrical eddy currents are created in all conductive materials. Conductive materials such as copper, aluminum and gold are those that readily move electricity. Solid wires of these metals create these resistant forces to electrical current flow. These resistant forces are called eddy currents.
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Apply a voltage into a single copper wire. As the individual electrons of the copper move the electrical charge along the surface of the wire, smaller electrical charges are formed. These smaller charges move in a rotational direction of clockwise and counterclockwise directions. The small eddy currents also create very small magnetic fields. These opposing magnetic forces create heat in the wire.
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Wrap more wires around the single wire and the eddy currents are lessened. These added wires or strands help to counter-effect the induced eddy currents. The more strands in a wire, the more canceling effect it can have on the errant magnetic fields. You may note that wires in household appliance cords and extension cords are made up of many small strands of wire. This is done to reduce eddy currents.
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Push the front doorbell button on your home. The small transformer that reduces the voltage to the button is made up of many small, thin insulated plates. The insulated plates reduce the eddy currents that can build up in a solid bar of metal. Over enough time of electrical power applied to a solid core, like a transformer, the metal would heat up and damage the wires wrapped around the metal. Malfunctioning transformers, with a damaged core insulation, begin to hum. This audible noise is a sign of eddy currents.
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Tips & Warnings
Eddy currents are used in many industrial applications. The most common is for stopping electrical motors. Hybrid electrical cars also use eddy currents to recharge onboard batteries. These batteries are re-energized during down hill coasts and braking.
