How Did The Magnetic Compass Work
Dec 18, 2024| A magnetic compass works based on the principle of the Earth's magnetic field.
1. The Basics of Earth's Magnetic Field
The Earth has a magnetic field that is similar to that of a bar magnet with a magnetic north pole and a magnetic south pole. The magnetic field lines run from the magnetic north to the magnetic south. The magnetic poles are not exactly at the geographic poles. The magnetic north pole is currently located in the Arctic region of Canada and is constantly moving.
2. The Structure of a Magnetic Compass
A typical magnetic compass consists of a magnetized needle. The needle is usually mounted on a pivot point so that it can rotate freely. The needle is balanced and often enclosed in a housing. The housing is usually marked with directions such as north, south, east, and west.
3. How it Works
The magnetized needle of the compass aligns itself with the Earth's magnetic field lines. The north - seeking end of the needle points towards the magnetic north pole of the Earth. So, when you hold a compass level, the needle will rotate until it is in a position parallel to the magnetic field lines, with the north - marked end of the needle indicating the approximate direction of the magnetic north.
To get the direction you want, you can use the markings on the compass housing. For example, if you know that the sun rises in the east and sets in the west, and the needle points to the magnetic north, you can determine other directions relative to the north - pointing needle. The direction 90 degrees clockwise from magnetic north is magnetic east, 180 degrees from magnetic north is magnetic south, and 270 degrees from magnetic north is magnetic west.
4. Magnetic Declination
There is a difference between magnetic north and true north (the direction towards the geographic North Pole). This difference is called magnetic declination. The amount of declination varies depending on your location on the Earth's surface. To get an accurate reading of true north using a magnetic compass, you need to know the magnetic declination for your area and make the appropriate correction. For example, if the magnetic declination in a certain area is 10 degrees west, you need to add 10 degrees to the magnetic north reading to get the true north direction.