The substances that attract iron magnetic materials to themselves are called magnets and the property of a magnet to attract ferromagnetic materials towards itself is called magnetism.
Type of magnet
There are mainly two types of magnets –
1. Natural magnets
Solids that are found independently in nature that have naturally magnetic properties are called natural magnets such as magnetite stones.
2. Artificial magnets
Magnets that are made by artificial methods are called artificial magnets. In these, the properties of magnetism can be reduced and increased at will. Artificial magnets are mainly made from metals like iron, cobalt, etc. Additionally, artificial magnets are also made using the magnetic effect of electric current.
The points where the highest magnetic properties are located near both the ends of any magnet are called magnetic poles. Each magnet has two poles. By hanging the magnet with a thread in the middle and hanging freely, one end of it stays towards the north and the other end towards the south. The tip facing north is called the North Pole and the tip facing south is called the South Pole.
Properties of magnets
- Magnetism has the highest properties at the poles of the magnet. As the center moves towards the center the magnetism property decreases and the magnetism property between the two poles becomes zero.
- Like any two magnets, poles repel each other and opposite poles attract each other.
- The two poles of the magnet cannot be separated. Regardless of the number of pieces of a magnet, each piece becomes a magnet and two poles are formed.
- Any magnet, tied with a thread in the middle and hung freely, always stays in the north-south direction.
The field around the magnet in which the properties of magnetism are found is called a magnetic field. The compass needle is deflected when it is brought into the magnetic field. If this compass needle is placed at some other point of the magnetic field, it rotates and becomes fixed in the other direction. The direction of the magnetic field is in the direction of the line drawn from the south pole of the compass needle to the north pole placed at some point in the field.
Magnetic field intensity
The force acting on the wire when a unit current flows in a coil of unit length placed perpendicular to the magnetic field of a magnet is called the intensity of the magnetic field at that location. It is a Vector sum and its unit is newton / ampere-meter or weber / square meter. If the intensity and direction of the magnetic field at each point of the magnetic field are equal in magnitude then the field is called a uniform magnetic field otherwise called an unequal magnetic field.
Magnetic force lines
Magnetic force lines are imaginary lines that continuously display the direction of a magnetic field. A tangent drawn to a point on these lines represents the direction of the magnetic field at that point. The magnetic force lines near a magnet are due to its magnetic field, while the magnetic force lines away from the magnet are due to the Earth’s magnetic field. There are two points between the magnetic force lines of the magnet and the earth where no magnetic force line passes. These points are called neutral points. The magnetic field of the magnet and the Earth’s magnetic field at neutral points are equal in magnitude and opposite in direction, so the resultant magnetic field at the neutral point is zero.
Properties of magnetic force lines
- The magnetic force lines always exit the north pole of the magnet and enter the south pole forming a curve and return through the magnet to the north pole. Thus the magnetic force lines move as a closed curve.
- Magnetic force lines never cross each other because two directions of the magnetic field at one point are not possible.
- At points where the strength of the magnetic field is high, the magnetic force lines are more close together and at points where the magnetic field strength is less, the magnetic force lines are far away.
- In a uniform magnetic field, the magnetic force lines are mutually parallel and at equal distances.