Oersted’s experiment

In 1820, French scientist Christian Oersted observed that the compass needle deflected from its initial direction, which is the north-south direction, in the presence of current-carrying wire. Oersted’s experiment is the first, which describes that current-carrying wire produces a magnetic field. The setup requires a planar coil of wire to deflect the magnetic needle vigorously along with the current of up to 1A. A classical setup is very difficult as it requires 10-20A. So, instead of that, we propose a low-cost type of aperture as a simple solution and practical modification of Oersted’s experiment. In this article, we elaborate on this experiment and try to understand how the magnetic field produces current. 

Body

We can understand this statement of the magnetic field due to current theoretically. 

Theoretical analysis is: 

1. A magnetic field of finite wire.
2. A magnetic needle in a magnetic field of wire.
3. A magnetic needle in the magnetic field of the earth.
4. A magnetic field in earth’s magnetic field and the wire .

But here, we have to study this statement experimentally by Oersted’s experiment.

Experiment 1

Aim: To determine the magnetic field by current-carrying source 

Material required: Copper wire, two-three cells of 1.5V each, a plug key, compass 

Procedure: Arrange the circuit in the proper manner for the flow of current.

• Place a copper wire in between the circuit and make sure that wire is parallel to the compass needle 
• Plug the key
• Observe the direction of the needle
• If the current flows from north to south, the north pole of the compass moves towards east and vice-versa
• Now, replace the connection that is current flows from south to north, and the needle will be deflected towards the west
• We will observe that the needle moves in the opposite direction from the initial one as it moves towards the west
• It means that the direction of the needle also changes when the flow of current changes
• Also, we observe the deflection of the needle in the compass by the flow of current in the copper wire

Experiment 2

Aim: To observe the magnetic field due to a current through a straight conductor 

Materials required: Battery, rheostat, ammeter, a plug key, long straight thick copper wire, rectangular cardboard, iron filings

Procedure: 

• Arrange the circuit for the flow of current
• Place rectangular cardboard between the circuit and make sure that cardboard should not move or slide up and down
• Insert the long straight thick wire parallel to the cardboard.  Connect the copper wire vertically between two points X and Y
• Sprinkle some iron filings on the cardboard uniformly
• Fix the rheostat and note the reading of current in the ammeter
• Plug the key for the flow of current in the copper wire
• The copper wire should be vertically straight
• Now tap the cardboard a few times
• Now observe the arrangement of iron filings
• We observe that iron filings arrange themselves in a concentric circle around the copper wire
• This concentric circle represents the magnetic field lines
• We can also find the direction of the magnetic field by placing a magnetic compass
• The north pole of the compass represents the direction of the magnetic field lines produced by the electric current through the straight wire
• It is also the same as the above experiment that the direction of magnetic field lines changes by changing the direction of the flow of current
• Besides this, the deflection increases on increasing the current
• Also, the magnetic circle increases as we move the compass from the copper wire and place it at a certain distance. Thus, this implies that magnetic field lines decrease when the current decreases and also when the distance increases

Right-hand thumb rule

It is an easier and better way of finding the direction of the magnetic field and electric current.

What is the right-hand thumb rule?

Imagine your right hand holding the current-carrying straight conductor in such a manner that your thumb should be pointed towards the direction of the current. Wrap your finger around the conductor in the direction of magnetic field lines. The finger’s direction shows the direction of the magnetic field, whereas the thumb direction shows the direction of the current.

Magnetic field due to current in a solenoid 

A solenoid is a circular turn of insulated copper wire which is wrapped closely in the shape of a cylinder. 

Now, the solenoid consists of magnetic field lines around themselves. The magnetic field line around the solenoid and the magnetic field lines around the magnet bar are the same. 

Here, your brain raises the question ‘why.’ 

It is because the solenoid behaves as a magnet such that its one end acts as the south pole and the other end behaves as the north pole.

Note: The field lines in the solenoid are arranged in straight parallel lines. Thus, this implies that magnetic field lines are the same at all points inside the solenoid, meaning the magnetic field is uniform throughout the solenoid. 

Points to remember:

1. The strength of the magnetic field is directly proportional to the number of turns and also to the magnitude of the current. The more the number of turns, the stronger is the magnetic field. 
2. The formula of the magnetic field due to the solenoid is B = 𝜇0 (NI/L), where N is number of turn in solenoid, I is the current passing through solenoid and L is the length of solenoid.

Principle of Oersted’s Experiment 

The principle of this experiment is to observe the magnetic field due to the current-carrying conductor.

This states that the electric current creates magnetic fields around them. This shows the relation between magnetism and electricity. 

• Faraday’s law of induction is also related to this experiment
• Magnetic field lines arrange in a plane perpendicular to the wire
• When the direction of the current is reversed, the magnetic field is reversed as well
• The strength of the magnetic field depends upon the magnitude of electric current as it is directly proportional to it
• The strength of the magnetic field is inversely proportional to the distance of the point of the wire

Conclusion

Here, we reach the end of the article, and we conclude that current-carrying conductors produce magnetic fields around themselves, and this is due to the moving electrons. But there is a drawback; the wire should be passed through the wooden stick or cardboard. The magnetic field produces when the current passes through the wire. This is observed when the needle gets deflected perpendicular to the wire. Also, when the direction of current is reversed, then the needle will also deflect in the opposite direction. Thus, changing the direction of the magnetic field. The strength of a magnetic field depends on certain factors; that is, it is directly proportional to the magnitude of current and inversely proportional to the distance between the wire magnetic field.