Friday, September 30, 2016

Earth magnetic field and bar magnet

Because of the nature of the earth, it behaves like a huge magnet with north and south pole lying at the geographic south and north of the earth. So a magnet can experience a magnetic field around it.

Let us assume a bar magnet is placed in such a way that its north pole is along the north of the earth. On the axial line, the earth magnetic field of the earth and the magnetic field of the magnet lies along the same direction so there will be some resultant magnetic field on the axial line. But along the equatorial line of the magnet, the earth magnetic field and the magnetic field of the bar magnet goes to opposite direction and at a particular point these two fields cancels each other and hence we get a point called neutral point on that line.

As it happens on the equatorial line, we can find the location of the neutral line as shown in the diagram below.

If the south pole of the bar magnet is along the north of the earth, neutral point is not on the equatorial line but on the axial line. We can show the direction of the magnetic field around the bar magnet as shown in the diagram below. In this case neutral point can be found using the concepts that were discussed in the previous case.

If two bar magnets are placed along a line such that their north poles are facing each other, then between them at a particular point, we can get a neutral point and at that point, resultant magnetic field is zero. The expression for that is as shown in the diagram below.

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