Theory
A magnetic field refers to magnetic control of electric currents and the magnetic materials, specified by both direction and strength. It results from moving electric charges and the magnetic moments of elementary particles related with their spin. It can also be defined as its force exerted on a charged particle in motion. Magnetic field lines normally form in concentric circles around a current currying conductor cylindrical in nature for example a length of wire. The strength of the magnetic field is inversely proportional to the length of the wire or the distance for an infinite length.
Biot–Savart law describes the magnetic field generated by a steady current, I to be equivalent to;
Where;
- dℓ refers to vector line element having magnitude similar to length of the piece of current directed in the direction of current.
- μ0 refers to magnetic constant.
- r refers to the distance between the location of vector line element and the point where the magnetic field is being calculated
- r̂ rerfers to the unit vector displacement in the direction of r
The Biot–Savart Law can be used for calculation of magnetic field along the axis of a loop. The direction of force experienced by a charge or current can be obtained by the principle of the right hand rule or the Flemings's left hand rule.
In cases where there exists more than one source of magnetic field, the resultant magnetic field becomes the vector sum total of each magnetic fields present in the sources along. When a charge carrier of a current currying conductor is placed in a magnetic field, it experiences a Lorentz force resulting into separation of charge, in direction that is at right angles to the magnetic field and the current.
Data Table
Section 1: The magnetic field at the center of a current carrying coil.
Field Coil Radius, R = 0.105 m Number of turns in Field Coil, N = 200
Section 2: The magnetic field along the axis of a current carrying coil.
Field Coil Current = 1.00 A
Questions
My graph from part one clearly shows that magnetic field strength is directly proportional to the current in the coil as expected. This is due to the nature of the equation that is used to find the magnetic force showing that increase in the current directly increases the force.
The slope of the magnetic field vs. current graph from part one is consistent with the expected value. This is because of the linear variation of the magnetic field and current when the graph is plotted.
In a case where the radius of one of the current carrying loop is twice that of another current carrying loop, and the net magnitude field is zero at the centre the magnitude and direction of current in the outer loop changes by half that of the smaller loop.
In part two, the magnetic field varies along the axis of the coil as expected but shows great discrepancy at the furthest position. This may be attributed to the change in temperature and pressure since such change in environment affects the flux density of the magnetic field.
Conclusion
The force experienced by a current carrying wire is similar to that of a charge in motion because a charge carrying wire is a combination of moving charges. It will experience a force in the presence of a magnetic field. Energy is required for magnetic field generation to work against electric field created by a charging magnetic field and also alter the magnetization of materials lying on the magnetic field.
According to my results, the magnetic field sensor voltage increases with the increase of current in the coil and vice versa. But for section two, as the sensor is moved away from the centre, along the x axis of the coil the voltage decreases. From the calculations, there exist some errors that could have resulted from not setting up the scale with the coil the same way. The distance of the coil from the magnetic field could affect the strength causing slight error. Therefore better results could be achieved through proper setting of the apparatus and accurate reading of the data.
Works cited
Aharoni, Amikam. Introduction to the theory of ferromagnetism. 2nd edition. Oxford
