Force of Attraction between Solenod and bar magnet

[soumaz07]

INTRODUCTION
A bar magnet is a rectangular block of a magnetized material moment of a magnet is the product of pole
Strength P and its length 2l i.e., m = p x 2l. A long closely wound helical coil is called a solenoid. When a current flows through a solenoid, each turn behaves as a magnetic dipole and the solenoid acts as a bar magnet with north pole at one end and south pole at the other. Through this project we try to find the relation between the force of attraction of bar magnet to the solenoid carrying current and the magnitude of current passing through the solenoid.

Aim
To investigate the effect on the force of attraction between a solenoid and a bar magnet when the current through the solenoid is changed.
METHOD OF STUDY
A physical balance is taken and its left pan is removed. Instead of left pan, a bar magnet is suspended with its south ole pointing downwards. Suitable masses are added in the weight pan to make the beam of the balance horizontal i.e., the equal oscillations of the pointer. The mass m, in the right pan is noted.
Connections are made as shown in the diagram. The solenoid is placed vertically below the bar magnet. The circuit is closed. A suitable current is passed through the solenoid by adjusting the rheostat. Since the magnet is attracted towards the solenoid, the beam of the balance is disturbed. Masses are added in the right pan so that the pointer oscillates equally on both sides. The right mass m2 on the right pan is noted. The additional mass (m2-m1) added on right pan balances the force of attraction experienced by the bar magnet (m2m1) g. gives the force of attraction ‘g’ is the acceleration due to gravity.
The experiment is repeated by the changing the current passing through the solenoid.
A graph is drawn with the current along the x-axis and force of attraction in Newton along y-axis.


Fig (h) picture I

COLLECTED DATA
a) Theory :-


Picture -2

Consider a solenoid carrying a current ‘i’ Let n be the number of turns of the solenoid per unit length,
(i) Filed at the mid point o of the axis of the solenoid:-
B= µon I along the axis.
(ii) Field at the ends P and Q of the solenoid along the axis:-
B=µ0 n I/2 half of the field at the mid point o.
Field at any point outside the solenoid is practically zero.

By the Lenz’s law, when N-Pole of the magnet is introduced into the coil, the induced current flows
In such a direction as to N-polarity to the end of the coil facing the magnet. Thus, since like poles repels, the motion of the magnet is opposed by the induced current.

When the magnet is withdrawn from the coil. The director of the induced current is reversed. The nearer end of the coil becomes a S-Pole and since, Unlike Poles attract, the motion of the magnet is opposed. Like this, in the reversed current condition the force of attraction between the magnet and the solenoid can be balanced by using suitable masses. Thus, the product of this mass (m) and acceleration due to the gravity (g) gives the quantity of force of attraction.
Thus, When a current flows through a solenoid each turn behaves as a magnetic dipole and the solenoid acts as a bar magnet with North Pole at one end and South Pole at the other.
The magnetic field B at a distance x along the axis of a circular5 coil of radius r carrying a current I is given by
B= µoIr2/2x3 = (µoI r2 / 2x3) 2 p/ 2 p= µo 2I A/4p x 3
Where A is the area of the coil. In this IA is the magnetic dipole moment m. Hence the direction A is perpendicular to the solenoid. Hence a current carrying solenoid can act as a magnetic dipole. M= IA, when area increases magnetic moment also increases .
Picture-3

On looking on the face of the current carrying solenoid, if the current flows anticlockwise, that exhibits north polarity. If the current flows clockwise, that faces exhibits south polarity.
The force of attraction between the bar magnet and the solenoid carrying current is directly proportional to the magnitude of current passing through the solenoid.
(b) Observations and data analysis
Value of one division on the ammeter= .05 A.
Mass in the right pan to balance mass of bar magnet

m1 = 33.33 gm
= 33.33 x 10 -3 kg.
graph
Table -1

CONCLUSION
Force-current graph is a straight line. This shows that the force of attraction between the bar magnet and the solenoid carrying current is directly proportional to the magnitude of current passing through the solenoid.

I just want to know that is this project perfect for a 12th standard.Plz give additional information on this topic.

[ChrisG]

Hi soumaz07,
Welcome back to the forums.

For other experts who will be assisting, here is the original text for this project:
http://www.indiastudychannel.com/projec ... agnet.aspx
I gather that the "12th standard" is the name given to the final year of secondary school in India.

I do not know the context of this project for you. Is this project for a school assignment or a science fair competition?

Looking forward to hearing more about your project.

Chris

[soumaz07]

It's a part of school assignment.Plz suggest some more experiments that can be done in the same experiment

[ChrisG]

Here is a variation you could try:
https://www.sciencebuddies.org/science- ... p025.shtml
You might need to adapt that project for your grade level.
Good luck!
Chris