Investing Earth’s Magnetism
If you're lost in the woods, your best chance of finding your way might be a tiny magnet.
A magnet is what makes a compass point north -- the small magnetic pin in a compass is suspended so thatitcan spin freely inside its casing and respond to our planet's magnetism.
A compass needle aligns itself and points toward the top of Earth's magnetic field, giving explorers and lost souls a consistent sense of direction.
Acompassis an instrument used fornavigationand orientation that shows direction relative to the geographiccardinal directions, or "points". Usually, a diagram called acompass rose, which shows the directionsnorth,south,east, andwestas abbreviated initials marked on the compass. When the compass is used, the rose can be aligned with the corresponding geographic directions, so, for example, the "N" mark on the rose really points to the north. Frequently, in addition to the rose or sometimes instead of it, angle markings in degrees are shown on the compass. North corresponds to zero degrees, and the angles increase clockwise, so east is 90 degrees, south is 180, and west is 270. These numbers allow the compass to showbearings, which is a term used in navigation.
The Earth’s north geographic pole (where Santa lives) is near the earth’s south magnetic pole. This is why a compass needle’s north end points to the north geographic pole (because compass’s north end points in the direction of the magnetic field).
How Does a Compass Work?
A compass points north becauseall magnets have two poles, a north pole and a south pole, and the north pole of one magnet is attracted to the south pole of another magnet. (You may have seen this demonstrated by a pair of simple bar magnets orrefrigeratormagnets pushed end to end.)
TheEarth is a magnetthat can interact with other magnets in this way, so the north end of a compass magnet is drawn to align with the Earth's magnetic field. Because the Earth's magnetic North Pole attracts the "north" ends of other magnets, it is technically the "South Pole" of our planet's magnetic field.
True north
While a compass is a greattoolfor navigation, it doesn't always point exactly north. This is because the Earth's magnetic North Pole is not the same as "true north," or the Earth'sgeographic North Pole. The magnetic North Pole lies about 1,000 miles south of true north, in Canada.
And making things even more difficult for the compass-wielding navigator, the magnetic North Pole isn't even a stationary point. As the Earth's magnetic field changes, the magnetic North Pole moves. Over the last century, it has shifted more than 620 miles (1,000 kilometers) toward Siberia, according to scientists at Oregon StateUniversity.
This difference between true north and the north heading on a compass is an angle called declination. Declination varies from place to place because the Earth's magnetic field is not uniform it dips and undulates.
These local disturbances in the field can cause a compass needle to point away from both the geographic North Pole and the magnetic North Pole. According to the United States Geological Survey, atvery high latitudes, a compass needle can even point south.
By using charts of declination or local calibrations, compass users can compensate for these differences and point themselves in the right direction.
Direction: Read the passage above and work on the Magnet and Compass Interactive Simulation before answering the following questions.
1.Describe the Earth as a magnet
Earth has a magnetic field that has a shape similar to that of a large bar magnet.
TheEarth is a magnetthat can interact with other magnets in this way, so the north end of a compass magnet is drawn to align with the Earth's magnetic field. Because the Earth's magnetic North Pole attracts the "north" ends of other magnets, it is technically the "South Pole" of our planet's magnetic field.
2.Compare the magnetic properties of the Earth to that of a natural or manufactured magnet.
South Pole of the Earth’s Bar Magnet attracts the north pole of the compass magnet.The magnetic field of Earth is generated by currents flowing in the liquid outer core region. Like all magnetic fields, it has a north and south polarity.
3.How is a compass used for navigation on land and sea
When the compass is used, the rose can be aligned with the corresponding geographic directions, so, for example, the "N" mark on the rose really points to the north. North corresponds to zero degrees, and the angles increase clockwise, so east is 90 degrees, south is 180, and west is 270. These numbers allow the compass to showbearings, which is a term used in navigation.
4.Explain how a compass works using the magnetic field of the Earth
The Earth’s north geographic pole is near the earth’s south magnetic pole. This is why a compass needle’s north end points to the north geographic pole (because compass’s north end points in the direction of the magnetic field).
5.Explain declination.
The difference between true north and the north heading on a compass is an angle called declination. Declination varies from place to place because the Earth's magnetic field is not uniform it dips and undulates.