How does a Magnetic Compass Work?

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How does a Magnetic Compass Work?

A compass is one of the simplest tools available, and is extremely practical. A compass is a device that shows the direction of north. Before GPS and other high tech navigational gadgets were invented, compasses were used to determine direction. Before compasses were available, many sailors determined their direction by the position of the stars, by the sun, etc. However, if the sky was cloudy or if it was dark, there would be no way of knowing which direction they were traveling. This had a considerable effect on traveling at the time and kept ships relatively close to shore.

With the advent of compasses, sailors were able to tell their direction and chart their travels much easier; this led to the age of explorers and ultimately the discovery of America.

How it Works

A compass is incredibly simple; it is a device that has a lightweight needle where at one end is a small magnet. This needle is attached to the device by a pivot that has very little friction allowing the magnet attached to the needle to move effortlessly. Since magnets always point north, a compass needle that is held steady will always point north. Usually on the device below the needle is a marking that states N for north or has a red mark which indicates north. Using a compass, you can easily view the direction in which north lies and deduce your current direction.

What Makes it Point North?

While a compass is a simple device, the underlying reason why a compass needle always points north tends to be the interesting question. Remember, compass needles have at the end of it a small magnet. Within the earth, there is a very strong magnetic force. You can think of the inside of the earth having a bar magnet that runs from the North Pole to the South Pole. In magnets opposites attract, so for the north end of a compass to point to the north, it would need to be attracted to the south end of the ‘bar magnet’.

So a compass simply picks up the slight force of the magnetic field within the earth. It should be noted that even though the magnetic force is strong within the center of the earth’s crust the surface is far removed from this field. By the time this force reaches the surface of the earth (possibly 8,000 miles), it is much weaker. In order for a magnet to pick up this force, it has to be allowed to move frictionlessly. Almost any resistance will stop the magnet from turning north.

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  1. dan said,

    on July 14th, 2009 at 12:04 am

    wow its amazing hahahahahaha!!!!!!!!!