Chapter 60 of 2364 min read
Bar magnet and magnetic field lines
Why this is asked: Magnetic field lines always form closed loops with no start or end point, since isolated magnetic poles don't exist — unlike electric field lines, which begin and end on charges. A bar magnet's field falls off as 1/r³, its axial value twice the equatorial one.
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- •An iron bar of length has magnetic moment . It is bent at the middle of its length such that the two arms make an angle of with each other. The magnetic moment of this new magnet is:
- •In a uniform magnetic field of 0.049 T, a magnetic needle performs 20 complete oscillations in 5 seconds. The moment of inertia of the needle is . If the magnitude of the magnetic moment of the needle is , then the value of is:
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