If the bar magnet in exercise 5.13 is turned around by 180º, where will the new null points be located?
Solution and Explanation
The magnetic field on the axis of the magnet at a distance d1 = 14 cm, can be written as:
\(B_1\) = \(\frac{\mu_0 2M}{4\pi (d_1)^3}\)=H ...(1)
Where,
M = Magnetic moment
\(\mu_0\) = Permeability of free space
H = Horizontal component of the magnetic field at d1
If the bar magnet is turned through 180°, then the neutral point will lie on the equatorial line.
Hence, the magnetic field at a distance d2, on the equatorial line of the magnet can be written as:
\(B_2\) = \(\frac{\mu_0 M}{4\pi (d_2)^3}\)=H ...(2)
Equating equations (1) and (2), we get:
\(\frac{2}{(d_1)^3}\)=\(\frac{1}{(d_2)^3}\)
\(\bigg(\frac{d_2}{d_1}\bigg)^3\)=\(\frac{1}{2}\)
∴ d2 = d1 × \(\bigg(\frac{1}{2}\bigg)^{\frac{1}{3}}\)
=14 × 0.794 = 11.1cm
The new null points will be located 11.1 cm on the normal bisector.
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Concepts Used:
Magnetism & Matter
Magnets are used in many devices like electric bells, telephones, radio, loudspeakers, motors, fans, screwdrivers, lifting heavy iron loads, super-fast trains, especially in foreign countries, refrigerators, etc.
Magnetite is the world’s first magnet. This is also called a natural magnet. Though magnets occur naturally, we can also impart magnetic properties to a substance. It would be an artificial magnet in that case.
Read More: Magnetism and Matter
Some of the properties of the magnetic field lines are:
- The lines and continuous and outside the magnet, the field lines originate from the North pole and terminate at the South pole
- They form closed loops traversing inside the magnet.
- But here the lines seem to originate from the South pole and terminate at the North pole to form closed loops.
- More number of close lines indicate a stronger magnetic field
- The lines do not intersect each other
- The tangent drawn at the field line gives the direction of the field at that point.