Magnetism is an invisible force, caused by the electrons in the atoms that make up everything around us. From your clothes to your desk, every bit of matter is made of tiny particles called atoms. Atoms have negatively charged electrons that spin around them. Most of the time, the electron spin in random directions. When all the electrons spin in the same direction, they create an invisible force known as magnetism.
A collapsed star, known as a neutron star, has the strongest magnetic force of any object in the universe.
A magnet is an object that has a magnetic field (an invisible pattern of magnetism). A magnet attracts or repels other items.
Magnets are usually made from iron or steel, but aluminum, steel-iron, copper, nickel, and cobalt can also be made into powerful magnets.
The below illustration shows a magnetic field or magnetic force distributed in the space around and within a magnet.
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1. Bar magnets – A magnet’s power is focused at the poles and lesser at the sides. Bar magnets are generally of the weakest shape because the poles have the smallest area. They are the most common shape used in everyday life such as refrigerator magnets and compasses. They are also commonly used for demonstrations in the classroom. These are the cheapest and the easiest magnets to replace.
2. Horseshoe magnets – Horseshoe magnets are just bar magnets bent in a U-shape. The U-shape makes the magnet stronger by pointing the poles in the same direction. Originally created as a replacement for the bar magnet, this shape has become the universal symbol for magnets. It can be used to pick up metal objects of any size depending on the strength of the horseshoe magnet. For example, small horseshoes can collect paper clips while industrial-sized horseshoe magnets are used in construction and engineering to pick up large pieces of heavy metal. Horseshoe magnets are also used at the bottom of the pendulum.
3. Disc magnets – By changing a magnet’s shape, we can increase the area of the poles, thereby increasing the strength of its pull. Because of the wide, flat surface, disc magnets have a large pole area making them strong, effective magnets.
Depending on the size of the disc, this shape has a variety of uses. Disc magnets are used every day in clothing, fashion accessories, and home décor. Sewing disc magnets into clothing is a great way to hold the fabric together. Industrial-sized disc magnets are commonly used to pick up old cars at junkyards.
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4. Sphere magnets – Sphere magnets are often sold as toys and novelty items. Sphere magnets make popular desk toys such as rattlesnake eggs. This shape can also be used to create bracelets and necklaces. Spherical magnets are also effective tools when demonstrating how some elements and molecules are structured if you use the spheres to represent atoms.
5. Coiled magnets – Magnets that are a helical coil of wire are called electromagnets, and they are some of the strongest magnets that exist. However, they only become magnetic when there is electrical current flowing through a wire into the magnet itself. The strength and polarity of the magnetic field created by the electromagnet is adjustable based on the current running through the wire. Electromagnets are used in moving parts such as CD players, DVD players, automatic windows, hard drives and automatic doors in supermarkets.
6. Cylindrical or Rod magnets – Cylindrical or rod magnets have a thickness which is equal or larger than their diameter. This enables the magnets to generate very high levels of magnetism from a relatively small surface pole area. Because of their shape, these magnets are ideal for educational, research and experimental uses.
7. Ring-shaped magnets – Most ring magnets are axially magnetized. North and south poles are located on the flat circular surfaces (“top and bottom”). The few diametrically magnetized ring magnets with poles “left and right” are specifically marked. Rings are similar to discs but are hollow in the center. Less volume means rings are not as strong as comparable discs, however, the hollow center makes them far more versatile – rings easily slide on to tubes or rods.
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There are three main types of magnets – temporary, permanent, and electromagnets.
Temporary – Some iron and iron alloys can be easily magnetized by even a weak magnetic field. However, when the magnetic field is removed, the object gradually loses its magnetism.
Permanent – Examples are alnico (Aluminum, Nickel Cobalt alloy) and ferrites (ceramic-like material that is made from a mix of iron oxides with nickel, strontium, or cobalt). Once they are magnetized, these objects do not easily lose their magnetism.
Electromagnets – These are used when a very strong magnet is necessary. Electromagnets are made by placing a metal core inside a coil of wire that is carrying an electrical current. The electricity going through the wire produces a magnetic field. While the electric current is flowing, the core acts as a strong magnet. Computers, TVs, and electric motors are electromagnets.
The common types of material that permanent magnets are made with are ceramic, alnico, and neodymium. Ceramic magnets are strong and work well for most experiments. Alnico magnets are even stronger and work very well for science experiments, although they are more expensive than ceramic magnets. Neodymium magnets are so strong that one a half-inch in diameter can lift several pounds of ferromagnetic objects. They are the most expensive of these three magnet types.
1. Attractive property – Magnet attracts ferromagnetic materials like iron, cobalt, and nickel.
2. Repulsive property – Each magnet has a south pole and a north pole. Like magnetic poles repels each other and unlike magnetic poles attract each other.
3. Directive property – A freely suspended magnet always points in a north-south direction.
The earth is a very big magnet, and there is a magnetic field all around us. It's North and South poles are highly magnetic. The Earth's North Pole is also a magnetic north pole: a compass points north towards the North Pole because it is attracted by the Earth's magnetic field.
At the center of the Earth spins the Earth’s core. The core is made up of mostly iron. The outer portion of the core is liquid iron that spins and makes the earth into a giant magnet. This is where we get the names for the north and south poles. These poles are actually the positive and negative poles of the Earth’s giant magnet. This is very useful to us here on Earth as it lets us use magnets in compasses to find our way and make sure we are heading in the right direction. It’s also useful to animals such as birds and whales who use the Earth’s magnetic field to find the right direction when migrating. Perhaps the most important feature of the Earth’s magnetic field is that it protects us from the Sun’s solar wind and radiation.
A compass has a tiny magnet in it. The arrow always points to the North Pole.
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