Why it is not advisable to slide a magnet on an iron bar back and forth during magnetising it?

Answer the following questions . a. Why does a paramagnetic sample display greater magnetisation (for the same magnetising field) when cooled ? b. Why is diamagnetism , in contrast , almost independent of temperature ? c. If a toroid uses bismuth for its core, will the the field in the core be (slightly ) greater or (slightly ) less than when the core is empty ? d. Is the permeability of a ferromagnetic material independent of the magnetic field ? If not, is it more for lower or higher fields ? e. Magnetic field lines are always nearly normal to the surface of ferreomgnet at every point . (This fact is analogous to the static electric field lines being normal to the surface of conductor at every point). Why ? f. Would the maximum possible magnetisation of paramagnetic sample be of the same order of magnitude as the magnetisation of ferromagnet ?

The I.Sc lecture theatre of a college is 40 ft wide and has door at a corner.A teacher enters t 12.00 noon through the door and makes 10 rounds along the 40 ft wall back and forth during the eriod and finally leaves the class - room at 12.50 p.m. through the samedoor. compute his average speed and average velocity.

Though Earth is acting as a huge bar magnet it is not attracting other ferromagnetic materials. Why? Give reasons.

Answer the following questions a. Explain qualitatively on the basis of domain picture the irreversibility in the magnetisation curve of a ferromagnet. b. The hysteresis loop of soft iron piece has a much smaller area than that of a carbon steel piece. If the material is to go through repeated cycles of magnetisation , which piece will dissipate greater heat energy ? c. 'A system displaying a hysteresis loop such as a ferromagnet , is a device for storing memory ? ' Explain the meaning of this statement. d. What kind of ferromagnetic material is used for coating magnetic tapes in a cassette player , or for building ' memory stores ' in a modern computer ? e. A certain region of space is to be shielded from magnetic fields . Suggest a method.

a. What happens if a bar magnet is cut into two pieces : (i) transverse to its length , (ii) along its length ? b. A magnetised needle in a uniform magnetic field experiences a torque but no net force . An iron nail near a bar magnet , however , experiences a force of attraction in addition to a torque . Why ? c. Must every magnetic configuration have a north pole and a south pole ? What about the field due to a toroid ? d. Two identical looking iron bars A and B are given , one of which is definitely known to be magnetised. (We do not know which one ) . How would one ascertain whether or not both are magnetised ? If only one is magnetised , how does one ascertain which one ? [Use nothing else but the bars A and B ]

Null points are obtained on the axial line , when the north pole of the bar magnet is pointing towards geographical south . Why ?

Your are provided with iron filings and a bar magnet withour labelling the poles of the magnet.Using this____ : Which part of the bar magnet attracts more iron filing? Why?

An iron needles is attracted to the ends of a bar magnet but not to the middle region of the magnet. Is the material making up the ends of a bar magnet different from that of the middle region?

Your are provided with iron filings and a bar magnet withour labelling the poles of the magnet.Using this____ : How will you identify the poles of tghe magnet?