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WEEKS 7 & 8
MAGNETIC FIELD
CONTENTS
- Magnets and its properties
- Magnetization and demagnetization
- Temporary and permanent magnets
- Theory of magnetization
- Magnetic flux
- Earth magnetic field
MAGNET AND ITS PROPERTIES
A magnet is any material that is capable of attracting other pieces of the same material as well as pieces of iron. A substance is said to be ferromagnetic if it is attracted by a magnet. Examples are iron, cobalt, Nickel, and certain alloys. Substances which cannot be attracted by a magnet are called non-magnetic material e.g. brass, wood, copper, and glass.
Properties of magnets
- The ends of a magnet where the attracting power is greatest are called the poles.
- A bar magnet suspended freely in a vertical plane called magnetic meridian comes to rest with its axis in the North-South direction. The part which points northwards is called the north seeking pole or North Pole while the opposite pole is called the South Pole
- Like poles of magnet repel each other while unlike poles attract each other.
- The polarity of a magnet can be tested by bringing both poles in turn nearer to the known pole of a suspended magnet. Repulsion indicates similar polarity. Attraction could be due to two unlike poles or a pole and a piece of un-magnetized material. Hence, repulsion is the only sure test for polarity.
MAGNETIZATION AND DEMAGNETIZATION
Magnetization is a process whereby a material is made to become magnetic. This can be achieved through any of the following methods:
Electrical method – A cylindrical coil wound with several turns of insulated copper wire is connected in series with a six- or twelve-volt electric battery and switch. A coil of this type is called a solenoid. A steel bar is placed inside the coil and the current is switched on for some time. On removing and testing the steel, it will be found to have been
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