Introduction

The space around a magnet in which the force of attraction and repulsion force can be detected is called its magnetic field. Magnetic field lines are a vector quantity. The magnetic field is an abstract entity.

Some charges can produce magnetic fields. While a fixed charge only produces an electric field, a moving charge produces both an electric field and a magnetic field. In unequal magnetic fields, the direction of the magnetic fields is different, while in equal magnetic fields, the direction is the same.

The force acting on a charged particle moving in a magnetic field is called magnetic lines of force. The lines along which a sample of iron powder will self-align are the magnetic field lines.

The SI unit of the magnetic field is Tesla (T), named after the great scientist Nikola Tesla. The smaller unit of measuring magnetic fields is gauss (G). 10,000 gauss or 10 kG = 1 Tesla (T).

Visualizing Magnetic Field Lines

The direction of the magnetic field at a point can be determined with the help of a magnetic needle. If a magnetic needle is brought near a magnet, the magnetic needle will rest in a specific direction. However, if the position of the magnet is changed, the needle will also move in a curved path. This proves that the magnetic field line takes the form of a curve. 

These curved lines that govern the movement of the magnetic needle are called magnetic field lines or lines of force. These magnetic field lines take the form of a closed curve.

The direction of the North Pole determines the direction of magnetic field lines.

Properties of magnetic field lines of force

1. Magnetic force lines always originate from the magnet’s north pole, making a curve and entering the south pole. They pass through the magnet’s south pole and again come back to the north pole, forming a circle around the magnet.
2. Two magnetic lines of force can never intersect because that would mean there are two directions, which is not possible.
3. Where the magnetic field is strong, the lines of the curve are close. When it is weak, the lines of the curve are further apart.
4. The lines of force of a uniform magnetic field are parallel and at equal distances.
5. Lines of force in a magnetic field are imaginary lines that show the surface direction of the magnetic field in that place. 
6. A tangent drawn at any point on the magnetic force lines shows the magnetic field’s direction at that point.

The history of the magnetic field:

The magnet was discovered by an elderly Cretan shepherd, himself called Magnet, who was grazing his sheep in northern Greece. He found stones that would stick to the iron lined soles of his shoes, and this is how he discovered magnetite. For many centuries after its initial discovery, magnetite was shrouded in superstition. It was believed to heal the sick, both scare away and attract evil spirits. 

William Gilbert of England was the first person to study the scientific properties of magnetics. He studied them for almost 17 years and even went on to discover magnetic and non-magnetic substances.

Some materials are attracted to magnets, while others are not. Magnetic materials like iron, nickel, cobalt, etc., may be used to make artificial magnets. Non-magnetic substances such as rubber, stone, glass, silver, aluminum are not attracted to magnets and cannot be used to make artificial magnets. 

One of the key properties of two magnetics is that opposite poles attract each other while the same poles repel each other. That is to say, north-south poles will attract each other, while north-north and south-south poles will repel each other.

The following experiments can confirm the magnetic behavior of the earth:

1. A freely hanging magnetic needle will always come to rest in the north-south direction. When the magnetic needle is placed in such a way that it is hung freely with a thread so that it can rotate, the south pole of the magnetic needle will come to rest pointing in the direction of the geographic south, while the north pole of the magnet will point in the direction of the geographic north. This proves a magnetic field is present in the earth.
2. The magnetisation of an iron rod when it is inserted into the earth. When an iron rod is buried in the earth in the north-south direction for a period of time, it begins to behave like a magnet. This is possible only if the earth itself is a powerful magnet so that when a rod made of magnetic material comes into close contact with it, it takes on some magnetic properties of its own.
3. When a bar magnet is placed so that its south pole is towards the geographical north, by drawing magnetic lines of force, a neutral point may be obtained on either side of the magnet. Similarly, if the magnet is placed in such a way that the north pole of the magnet is towards the geographic south, then, in this case, the axial point is obtained by drawing magnetic lines.

Solenoids

A solenoid is an arrangement formed by wrapping a copper wire on a glass or cardboard tube in a spiral form. A solenoid can act as a powerful rod magnet when a current is passed through it. 

The greater the number of turns of the conductor wires on the solenoid, the greater the power of the magnet. The north pole and south pole of a solenoid magnet are formed according to the direction of the current. 

Properties of the magnetic field lines inside the solenoid: 

The strong magnetic field produced by a solenoid results in magnetic field lines. The magnetic field lines in the solenoid resemble parallel straight lines. 

The magnetic field is the same at all points inside a solenoid, which means a uniform magnetic field inside the solenoid. This magnetic property of the solenoid is used. 

Conclusion

Magnetic fields are an essential factor in understanding many aspects of life on earth, including the navigation of ships and the movement of climate systems across the earth’s surface. To understand natural phenomena better, magnetic field lines offer a very usual visualization method that allows scientists to determine the effects of the earth’s magnetic field on day-to-day human life and natural phenomena on the planet. 

The study of magnetic fields is an exciting area of research in physics. Exciting developments will continue in the study of magnetics for decades to come. For example, findings using pulsed-field magnets that operate at high altitudes, equipped with tools that take full advantage of electronics development, could take research in the field into thrilling new directions.