In this page we have explained about the magnetic field and magnetic field lines . Hope you like them and do not forget to like , social shar
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When we bring two magnets near each either they attract each other or they repel each other.
We can explain this force of attraction and repulsion between two magnets using the concept of Magnetic Field.
Magnets produces magnetic field in the space around it, which exerts force on any other magnet placed in this region. So it is the region around magnet within which its influence can be experienced.
What is magnetic Field?
The space around a magnet in which the force of attraction and repulsion due to the magnet can be detected is called the magnetic field.
IMPORTANT NOTE:- Each point in the field of any magnet has a particular strength and magnetic field at each point has definite direction. How do you find the direction of the magnetic field due to magnet at a point near it?
The direction of the magnetic field due to a magnet at a point near it can be found by placing a magnetic compass at that point. The compass needle gets deflected when it is placed near the magnet.
More about compass
The simplest compass is a magnetized metal needle mounted in such a way that it can spin freely.
Needle of a compass is a small bar magnet. This is the reason it gets deflected when we place it in the field of other magnet.
Compass needles are lightweight because earth has very week magnetic field. To show up the effect of that tiny magnetic field it should have even less effect due to gravity (note:- that gravitational force is much stronger then the force produced by earth’s magnetic field).
Compass needles are mounted on frictionless bearings because in this case there would be less frictional resistance for the magnetic force to overcome.
The ends of a compass needle points approximately in North and south directions.
About earth’s magnetism
The earth has a magnetic field which we call as the earth’s magnetic field.
The magnetic field is tilted slightly from the Earth’s axis.
The core of earth is filled with molten iron (Fe) which give Earth its very own magnetic field.
This large magnetic field protects the Earth from space radiation and particles such as the solar wind.
The region surrounding Earth where its magnetic field is located is termed as the Magnetosphere.
Earth has a magnetic field that has a shape similar to that of a large bar magnet.
To the north is the magnetic north pole, which is really the south pole of Earth’s bar magnet. (It is because this pole attracts the north pole of the compass magnet)
Magnetic Field Lines
Magnetic field surrounding the magnet and the force it exerts are depicted using imaginary curved lines with arrow called magnetic field lines.
Ways of obtaining magnetic field lines around a bar magnet
(A) Iron filings demonstration
Fix a sheet of white paper on a drawing board using some adhesive material.
Place a bar magnet in the centre of it.
Sprinkle some iron filings uniformly around the bar magnet (Fig. 2). A salt-sprinkler may be used for this purpose.
Now tap the board gently.
Iron filings near the bar magnet align themselves along the field lines.
This happens because the magnet exerts its influence in the region surrounding it. Therefore the iron filings experience a force. The force thus exerted makes iron filings to arrange in a pattern. The lines along which the iron filings align themselves represent magnetic field lines. (B) Demonstration using magnetic compass
With this demonstration you can draw the field lines of a bar magnet yourself
Procedure of this activity:-
Take a small compass and a bar magnet.
Place the magnet on a sheet of white paper fixed on a drawing board, using some adhesive material.
Mark the boundary of the magnet.
Place the compass near the north pole of the magnet.
Here you will notice that the south pole of the needle points towards the north pole of the magnet. The north pole of the compass is directed away from the north pole of the magnet.
Mark the position of two ends of the needle.
Now move the needle to a new position such that its south pole occupies the position previously occupied by its north pole.
In this way, proceed step by step till you reach the south pole of the magnet as shown in Fig. 3.
Join the points marked on the paper by a smooth curve. This curve represents a field line.
Repeat the above procedure and draw as many lines as you can. You will get a pattern shown in Fig. 4. These lines represent the magnetic field around the magnet. These are known as magnetic field lines.
Observe the deflection in the compass needle as you move it along a field line. The deflection increases as the needle is moved towards the poles.
There is one other simulation link that you can use to visualise the field of the bar magnet.
Click to Run
How to run this simulation
On clicking the 'click to run' button you will be asked to download a file(java file .jnlp). Once you download the file run the file and observe the magnetic field lines due to bar magnet. Please note that you need to have java installed in your system. For getting java you can visit this link
Direction in which compass needle points is the direction of the magnetic field.
The strength of the magnetic field is inversely proportional to the distance between the field lines.
Magnetic field lines never cross each other. It is unique at every point in space.
Magnetic field lines begin at the north pole of a magnet and terminate on the South Pole.
Properties of magnetic field lines
All field lines are closed curves.
Outside the magnet field lines emerge from North Pole and merge at South Pole.
Inside a magnet, the direction of field lines is from South Pole to its north pole.
Field lines never intersect each other.
Field lines are closed together near the poles and spread out away from them.
The field is stronger where the field lines are more closely spaced. So, the field is stronger near the poles then at other points.
Why do field lines never intersect each other?
If two lines were to intersect each other, then a compass needle placed at the point of interaction would point in two different directions which is not possible.
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