# Get the Knowledge that sets you free...Science and Math for K8 to K12 students

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## Magnetism

Magnetic therapy – a non invasive healing technique. The term “magnet therapy” refers to the use of static magnets placed directly on the body, generally over regions of pain. A static magnet is an ordinary permanent magnet. Static magnets are either attached to the body by tape or encapsulated in specially designed products such as belts, wraps, or mattress pads, etc. The pain gets reduced after placing magnets (or) Germ stone magnets on the regions of pain. This is a modern therapy, which is now being used all over the world, to reduce stress and pain, in a natural way. Lets learn more of such applications of magnets in this topic.

## After completing the topic, the student will be able to:

• Discuss and discover the characteristic properties of magnets and explore its applications in real life.
• Discover the laws of magnetism and determine the magnetic field around a magnet.
• Distinguish between electric field and magnetic field and their relevance in daily life.
• Investigate the induced magnetic effects of magnets while making a magnet using different methods.
• Apply the theory of magnetism in making new magnets from different materials having different magnetic domains.
• Demonstrate the existence of earth's magnetic field and its importance in finding the directions in any given place.
• Understand how the satellites are launched in the space, based on the direction of earth's magnetic field.
Metal scrap heap A large disc like electromagnet suspended on chains & manipulated by a crane. The magnet is used to separate & lift heavy objects from among the waste.
Magnetism

In our childhood, most of us might have come across a few objects that attracted pins, needles, blades, etc. We realized that they did not attract things like paper, wooden blocks, plastic scales, etc. Later, we learnt that such objects belonged to a class called magnets. In this chapter we will study the properties of magnets.

Naturally occurring magnets such as loadstones have been known to human being for more than two to three thousand years. Magnets are substances that attract some other substances and are generally made up of iron. Nickel also shows magnetic behavior some times. Alloys of Fe–Ni and few other elements added to them show magnetism. Some rare earth elements also show high magnetism. Alloys of samarium–cobalt are used as permanent magnets in many laboratories.

The idea that a magnet produces a magnetic force field in its neighbourhood is perhaps easier to comprehend than the concepts of gravitational and electric force fields. If we try to bring two like magnetic poles together, we see the repelling force between the two even when they are at some distance from each other. We observe that freely suspended magnets come to rest along the north–south direction due to the effect of the earth’s magnetic field.

Magnetic field Bar magnet with iron filings aligned around it. The magnetic field induces magnetism in each of the filings, which then line up in the field. Although the field is actually continuous, interactions between the filings cause them to accumulate in thin arcing lines.
Properties of magnets

To understand the properties of a magnet, try and do the following:
Suspend a bar magnet horizontally with the help of a string. When you disturb the magnet, you will observe that the magnet starts oscillating. After some time, it comes to rest in the same direction in which it was undisturbed.

Repeat the experiment. If you watch the magnet's direction carefully you will notice that the magnet always comes to rest in the earth's north–south direction. It is one of the inherent properties of magnets. On all bar magnets, the end that points to the earth's north is called the north pole – it always marked with a white dot. The other end, pointing towards the Earth's south is called the south pole. A magnet thus shows directional property. It can be stated as: when a bar magnet is suspended freely, it always comes to rest in a north–south direction.