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A bar magnet of length $3\, cm$ has points $A$ and $B$ along its axis at distances of $24 \,cm$ and $48\, cm$ on the opposite sides. Ratio of magnetic fields at these points will be
A bar magnet of length $3\, cm$ has points $A$ and $B$ along its axis at distances of $24 \,cm$ and $48\, cm$ on the opposite sides. Ratio of magnetic fields at these points will be
Updated On: Jun 23, 2023
- 8
- $\frac{1}{2\sqrt{2}}$
- 3
- 4
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The Correct Option is A
Solution and Explanation
Magnetic field due to a bar magnet at a distance r from the centre of magnet on axial position
$=\frac{\mu_0}{4\pi} \cdot \frac{2M}{r^3}$
$\therefore \frac{B_1}{B_2}=\Bigg(\frac{r_2}{r_1}\Bigg)^3=\Bigg(\frac{48}{24}\Bigg)^3$
$ =\frac{8}{1}=8$
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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.
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