Physics

### Definition Based Problems

Q 3202534438

Tho identical looking iron bars A and Bare given, one of which is definitely known to be magnetised. (We do not know which one.) How would one ascertain which one? [Use nothing else but the bars A and B.]

Solution:

Let, two bars are A and B. Now, bring one end of A near to B, and move it slowly (from one end to the middle). If force experienced by bar A reduces as we move towards middle, then bar B is magnetised, and A is not. If A experiences repulsion, then both the bars are magnetised.
Q 3262034835

Define magnetic susceptibility of a material. Name two elements, one having positive susceptibility and the other having negative susceptibility. What does negative susceptibility signify?

Solution:

Magnetic susceptibility is the property of a material which determines how easily it can be magnetised when kept in the magnetising field.

Or

Magnetic susceptibility is the ratio of the intensity of magnetisation (M) produced in the material to the intensity of magnetising field· (H).

 chi_m = M/H

Positive susceptibility : paramagnetic material e.g. Al , Ca.

Negative susceptibility : diamagnetic material e.g. Bi, Cu.

The negative susceptibility signifies that the material is diamagnetic in nature.
Q 3252534434

What are permanent magnets? Give one example.

Solution:

Permanent magnets are the materials which retain their ferromagnetic properties for a long time at room temperature, e.g. a bar magnet.
Q 3282034837

Draw a plot showing the variation of intensity of magnetisation with the applied magnetic field intensity for Bismuth. Under what condition does diamagnetic material exhibit perfect conductivity and perfect diamagnetism?

Solution:

The intensity of magnetisation (M) versus the magnetic field intensity (H) for bismuth. At very very low temperature, the material exhibits the perfect conductivity. On supercooling, the material exhibits perfect diamagnetism.