Concept explainers
The lightweight glass sphere in FIGURE Q29.1 hangs by a thread. The north pole of a bar magnet is brought near the sphere.
a. Suppose the sphere is electrically neutral. Is it attracted to, repelled by, or not affected by the magnet? Explain.
b. Answer the same question if the sphere is positively charged.
(a)
The effect of a bar magnet on a glass sphere placed near it.
Explanation of Solution
Given Info:
A glass sphere is hanging from a thread and North Pole of a magnet bar is brought near it.
Since magnetic materials are generally made up of iron and other metals. Moreover, this arises because of intrinsic magnetic moment present in the electrons called as electron spin; but here the material is glass and it happens to be an insulator. Hence, glass is not a magnetic material. Therefore, there is no effect of bar magnet over the glass sphere.
(b)
The effect of a bar magnet over a positively charged glass sphere placed near it.
Explanation of Solution
Given Info:
A positively charged glass sphere is hanging from a thread and North Pole of a magnet bar is brought near it.
There is no magnetic force between the glass sphere and bar magnet since they act on moving charges and other metals. There is a weak attraction due to polarization of charges present on the surface of glass if a magnetic bar is present.
Conclusion:
a) No, there is no attraction or repulsion between the glass sphere and the bar magnet.
b) Yes, the charges present on the glass surface are somewhat attracted to bar magnet.
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