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Q & A: Magnetic fields

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Most recent answer: 10/22/2007
Q:
I have two questions. 1. how do you measure a magnets strenght? 2. how do you calculate a magnets’ magnetic field span?
- ZO (age 13)
Texas
A:
One way of measuring the strength of a magnetic field of a magnet is to use an electronic device that measures the flux of the magnetic field. Flux can kind of be thought of as the density of "magnetic lines" that sit around the magnet. A more practical way to measure the strength of a magnet is to see from how far away it will pull in a piece of metal. A piece of metal on the ground is constantly subjected to the force of gravity. For the magnet to lift the metal off the ground, it would have to overcome this force (use a light piece of metal). This experiment relates to your second question too. The span of a magnetic field goes on forever; however, it becomes so weak that is completely unnoticable outside of a certain range. Depending on the shape, size and type of magnet you have will more or less determine the range of its field.

(published on 10/22/2007)

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