Presentation on theme: "NEETI SANON www.udgamschool.com Any substance which attracts pieces of iron towards itself. And always comes to rest in N-S direction is known as."— Presentation transcript:
Any substance which attracts pieces of iron towards itself. And always comes to rest in N-S direction is known as a magnet.
The Property of a magnet to attract things made up of Iron, Cobalt or Nickel is known as magnetism.
The area surrounding the magnet in which magnetic force is exerted to attract iron is known as magnetic field. The magnetic lines of force originate from the North Pole of a magnet and end at its South Pole.
The ends of the magnet where the magnetic force is concentrated are called magnetic poles. Each magnet has 2 poles : North & South pole.
There are 2 types of magnets : 1) Natural Magnets: They have low magnetic power. Eg : Magnetite, lodestone. 2) Artificial Magnets : They have a strong magnetic power. They are found in different shapes.
A natural magnet attracts certain materials: 1. Cobalt 2. Nickel 3. Iron 4. Steel 5. Alloys of any of the above These materials are called Magnetic materials.
1. They attract magnetic materials 2. A freely suspended magnet always rests in N-S direction. 3. Like poles repel, Unlike poles attract
Like Poles repel ! Unlike Poles attract !
Permanent magnet Soft-iron bar Permanent magnet brought Soft-iron bar becomes an near to soft-iron bar induced magnet In magnetic induction, an opposite pole is always induced. – 2 unlike poles facing each other is observed during magnetic induction. S N
The “free poles” near the end of magnets repel each other. As time passes, the magnet becomes weaker To prevent this weakening, bar magnets are stored in pairs by using keepers – 2 pieces of soft iron across the ends of the bar magnets.
Electromagnetism P Place the steel object inside a coil of wire (a solenoid). Pass a direct current through the solenoid. A magnetic field is produced on the solenoid. The steel rod is now placed inside a magnetic field. When the current is turned off the steel rod is found to be magnetized
Right-hand Rule. – Wrap the fingers around the coil form in the direction of the current flow in the solenoid. – the thumb will point in direction indicating the end which becomes the N- pole.
We know that at the centre of the Earth lies a molten metallic iron rich core. The outer portion of this core is molten. We also believe that this core is spinning. It is believed that the metals in the core have many loosely bound electrons and that these particles can conduct electricity. It is this mass of moving electrons which produces the magnetic field.
Think of the Earth as having a gigantic bar magnet buried inside. In order for the north end of the compass to point toward the North Pole, you have to assume that the buried bar magnet has its south end at the North Pole.
This method is derived from applying the processes of Magnetic induction – Note the polarities of both the permanent magnet & steel bar that is to be magnetized – This form of magnetism gained is weak but permanent
Two permanent magnets are used in this method. – Note of the polarities of the permanent magnets & their induced ends of the steel bar – This form of magnetism gained is also weak but permanent.