Explaining the behaviour of current loop as a magnetic dipole | STUDENT BABA

We all love playing with magnets, but have you ever heard about how a current loop behaves like magnetic dipole or a magnet. What would be its behaviour? So let's understand the behaviour of the current loop as a magnetic dipole.



Current loop behaves likes a magnetic dipole and has a magnetic field. They behave just like a magnet. Interesting part is, it depends upon the direction of current in loop which decides whether magnetic field line is in outward or inward direction. 

With the help of this outward and inward direction of magnetic field, North and South poles get decided. Anticlockwise direction of current creates north pole (outward direction magnetic field) and clockwise direction of current creates a south pole (inward direction magnetic field ).

As said earlier, the direction of current in loop decides the direction of the magnetic field, but during my research on this I came across some other things which you must know.

Behaviour of the current loop as a magnetic dipole:

So we already know that current loop as a magnetic dipole behaves like a magnet. The direction of current in the loop whether it's clockwise or anticlockwise decides the magnetic field lines direction.

The direction of magnetic field lines is decided by the direction in which current is flowing. If it's in anticlockwise then direction of magnetic field line will be in outward direction but if it's in clockwise direction it will in inward direction. 

I know it can bit confusing for you in anticlockwise and clockwise language. Don't worry same goes for me too, until I found this easy tip to remember it. See the image below:

Direction of magnetic field lines in a current loop
Direction of magnetic field lines in a current loop

The way the letters 'S' and 'N' are written you can note down that it shows the direction of current flowing which helps us to remember this easily that anticlockwise direction shows north pole whereas clockwise direction of current creates south pole.

The direction of magnetic field lines whether it's outward or inward is shown by wood screw head and wood screw point shown below:

Direction of magnetic field lines in a current loop
Direction of magnetic field lines in a current loop

Wood screw head sign shows that direction of screw is inward because we are not able to see pointed part of screw and so direction is inward. This inward direction of screw denotes the direction of the magnetic field. 

Whereas wood screw point shows the direction of magnetic field lines is in outward direction. Screw head side shows magnetic field is in inward direction whereas pointed side shows the direction is in outward direction.

Current loop as a magnetic dipole:

We know that moving current produces magnetic field according to Biot-Savart's law:


Biot-Savart's law gives the value of magnetic field created due to small segment of current-carrying conductor at a specific point in the space.

Current in the circular coil produces magnetic field and amperes found out that magnetic field created due to circular coil is similar to the magnetic field due to a bar magnet.

Bar magnet and current loop
Bar magnet and current loop

This can be due to deflection shown by the magnetic needle was same when brought near bar magnet and current carrying coil. Magnetic field was showing same deflection by both of them.

Due to this evident amperes demonstrated that how a solenoid (coil made up of more than 2 current carrying circular coil) is same as the bar magnet. This drives us to the conclusion that :

A current carrying circular coil has magnetic dipole 

Behaviour of the current loop as a magnetic dipole:

Current loop as a magnetic dipole behaves like magnet. It has magnetic field lines as well as north and south pole just like a bar magnet.

To put all this in simpler perspective, imagine a clock. Now clock completes one round from 12 - 12. That direction is what we called as clockwise. So if current is clockwise direction then the direction of magnetic field lines will be in inward direction.

Similary, direction opposite to movement of clock is called anti-clockwise direction. So if current is moving in anti-clockwise direction then direction of magnetic field lines will be in outward direction.

i.e If current is in anti-clockwise direction then direction of magnetic field lines will in outward direction. If current is in clockwise direction then direction of magnetic field lines will in inward direction.

Conclusion:

Current loop behaves like bar magnet because magnetic field created by bar magnet and current loop shows same amount of deflection in magnetic needle when brought near.

The direction of magnetic field lines depends upon the direction of current of flow in current loop. 
If it's in anti-clockwise direction then loop behaves like north pole and direction of magnetic field line will be outward

Whereas if current is flowing in clockwise direction then loop behaves like south pole and direction of magnetic field lines will be inward.


F.A.Q:

Q.1 Why current loop behaves like magnetic dipole ?

Moving current creates magnetic field and therefore when there is current in loop it behaves like magnet or magnetic dipole.

Q.2 If current is in clockwise direction then will the loop have only south pole or if current is in anti-clockwise will it have only North pole ?

No, loop will have both the poles of magnet. If current is flowing in clockwise direction then that side will behave as south pole and if you see it from other end, current direction will be anti-clockwise so it will behave like north pole.

It's just that from which side we are viewing the loop.

Q.3 Is it possible to separate north and south pole ?

No its not possible to separate north and south pole. For example if you cut the bar magnet it will be separated into two different pieces but it's piece will have its own north and south pole.

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    1. Hello, thanks for your comment. Can you please tell me, what exactly is wrong? I really appreciate your help.

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