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What is a magnet ?Any substance which attracts pieces of iron towards itself.
And always comes to rest in N-S direction is known as a magnet.
What is magnetism ?The Property of a magnet to attract things made up of Iron, Cobalt or Nickel is known as magnetism.
What is Magnetic Field?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.
Magnetic Field?
Magnetic Poles
The ends of the magnet where the magnetic force is concentrated are called magnetic poles.
Each magnet has 2 poles : North & South pole.
Types of MagnetsThere 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.
Artificial Magnets
Types of Magnets
Magnetic Compass
Magnetic SubstancesA natural magnet attracts
certain materials:1. Cobalt2. Nickel3. Iron4. Steel5. Alloys of any of the aboveThese materials are called
Magnetic materials.
Properties of a Magnet
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 !
Laws of Magnetism
Unlike poles Attract,
Like poles Repel
Poles of a magnet alwaysCome in pairs!
If you cut a magnet in half,
S N S N S N
Induced Magnetism
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
S N S N
Storage of Magnets - Using Keepers
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.
ElectromagnetismPPlace the steel object inside a coil of wire (a solenoid).• Pass a direct current through the solenoid.• A magnetic field isproduced 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
Electromagnetism
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.
Earth is a big Magnet
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.
Magnetization by Stroking(Single-Touch)
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
Magnetization by Stroking (Double-Touch)
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.
