by Ron Kurtus (revised 29 January 2013)
Magnetism is a force of attraction or replusion that acts at a distance. It is due to a magnetic field, which is caused by moving electrically charged particles. It is also inherent in magnetic objects such as a magnet. A magnet is an object that exhibits a strong magnetic field and will attract materials like iron to it. Magnets have two poles, called the north (N) and south (S) poles. Two magnets will be attacted by their opposite poles, and each will repel the like pole of the other magnet. Magnetism has many uses in modern life. Questions you may have include:
* What is a magnetic field?
* What is a magnetic force?
* What is the relationship between magnetism and electricity? This lesson will answer those questions.
A magnetic field consists of imaginary lines of flux coming from moving or spinning electrically charged particles. Examples include the spin of a proton and the motion of electrons through a wire in an electric circuit. What a magnetic field actually consists of is somewhat of a mystery, but we do know it is a special property of space.
Magnetic field or lines of flux of a moving charged particle Names of poles
The lines of magnetic flux flow from one end of the object to the other. By convention, we call one end of a magnetic object the N or North-seeking pole and the other the S or South-seeking pole, as related to the Earth's North and South magnetic poles. The magnetic flux is defined as moving from N to S. Note: The Earth does not follow the magnetic configuration in the aboce illustration. Instead, the lines of flux are opposite from a moving charged particle. Confusion About the North Magnetic Pole
by Ron Kurtus (28 January 2013)
As you know, the N-end of a compass points toward the Earth's North Magnetic Pole and the N-pole of a bar magnet repels the N-end of a compass. However, designating the ends of a compass and bar magnet as N and S has brought about confusion regarding the actual direction of the Earth's magnetic field. The present convention is that the North Magnetic Pole of the Earth is the south pole of the magnetic substance of the Earth's core. Likewise, the South Magnetic Pole is the north pole of the magnetic substance. Questions you may have include:
* How was the Earth's North Magnetic Pole named?
* How were magnet poles named?
* What is the prevailing naming convention?
This lesson will answer those questions.
When it was discovered that the Earth had a magnetic field coming from near the North and South Poles, it was assumed that the Earth was like a huge magnet with North and South Magnetic Poles. Compass points north
The end of a compass that pointed toward the North Magnetic Pole was called the north-seeking end of the compass. Likewise, the end of a bar magnet that repelled the north-seeking end of a compass was called the north-seeking pole of the magnet. However through the years, magnets were labeled with N and S ends, and people soon simply called them the north and south poles of the magnet. Designation of Earth's magnet changed
But if the north pole of a bar magnet and of a compass were attracted to the North Magnetic Pole, then the polarity of the North Magnetic Pole must really be south!
Earth's magnetic field designation
This was confusing, but scientists felt that it was easier to say the Earth's internal magnet had its south pole facing the North Magnetic Pole than to try to change the way the public called their magnets. Note: This situation is similar to that in electricity, where by convention electrical current goes from positive (+) to negative (−), but electrons move in the opposite direction in a wire. Summary
The N-end of a compass points toward the Earth's North Magnetic Pole and the N-pole of a bar magnet repels the N-end of a compass. However, designating the ends of a compass and bar magnet as N and S brought about the...