A uniform conducting wire of length 12 a and resistance R is wound up as a current carrying coil in the shape of
(i) an equilateral triangle of side a,
(ii) a square of sides a and
(iii) a regular hexagon of side a. The coil is connected to a voltage source V_0. Find the magnetic moment of the coils in each case.
The different shapes form figures of different area and hence, their magnetic moments vary.

The vertical component of the earth's magnetic field at a place is \(0.24\sqrt { 3 } \times { 10 }^{ -4 }T\) . Find out the value of horizontal component of the earth's magnetic field, if angle of dip at that place is \({ 30 }^{ \circ }\) .

A solenoid of 600 turns per meter is carrying a current of 4A. Its core is made of iron with relative permeability of 5000. Calculate the magnitudes of magnetic intensity, intensity of magnetisation and magnetifield inside the core.

Answer the following questions:
i) Explain qualitatively on the basis of domain picture the irreversibility in the magnetisation curve of a ferromagnet
ii) The hysteresis loop of a 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?
iii) A system displaying a hysteresis loop such as a ferromagnet, is a device device for storing memory. Explain the meaning of this statement.
iv) What kind of ferromagnetic material is used for coating magnetic tapes in a cassette player or for building 'memory stores' in a modern computer?
v) A certain region of space is to be shislded from magnetic fields, Suggest a method.

A bar magnet of magnetic moment m and moment of inertia I (about a center, perpendicular to the length) is cut into two equal pieces, perpendicular to the length. Let T be the period of oscillations of the original magnet about an axis through the midpoint, perpendicular to the length, in a magnetic field B, what would be the similar period T^' for each piece?