Tip 1: Field due to a bar magnet
What will be the field around a bar magnet of pole strength m and length 2l?
At an axial point the field due to a bar magnet is given by the resultant of field due to North Pole, and field due to South Pole,
For a small bar magnet, l<
where is the magnetic moment()
At an equatorial point, the field is given by,
for small bar magnet, l<
Now, How will you find the field die to a bar magnet at any arbitrary point?
Let's simplify the steps to find the field due to a bar magnet.
- Determine the distance r at which the field is supposed to be calculated. is the vector between the point P and the center of the bar magnet making an angle with the magnet.
- Resolve magnet N-S into N'-S' and N"-S" so that we can assume P to be in axial position for N'-S' and in equatorial position for N"-S".
- The magnetic moment can be resolved as along the axial line, N'-S'. Similarly, magnetic moment can be resolved as along the equatorial line of N"-S"
- Field due to N'-S' can be written as,
Field due to N"-S" can be written as,
- Net field can then be found as a resultant of and
A bar magnet has pole strength and is placed as shown in Fig. (a). Find the magnetic field at .