A magnetic needle is suspended freely so that it can rotate freely in the magnetic meridian. In order to keep it in the horizontal position, a weight of 0.2 g is kept on one end of the needle. If the pole strength of this needle is 20 Am, find the value of the vertical component of the earth s magnetic field, `(g = 9.8 m//s^-2)`

A magnet makes 55 vibrations in one minute where horizontal component of earth's field is 0.36G. If the moment of inertia of the bar magnet is 10^-5 Kgm^2 , find the magnetic moment of the bar magnet.

A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian, has its north tip pointing down at 21^@ 48^1 with the horizontal. If the horizontal component of the earth's magnetic induction at that place is 3.5 xx 10^-5 T, determine the earth's magnetic induction at that place.

A stone of mass 1 kg is whirled in horizontal circle attached at the end of a 1 m long string. If the string makes an angle of 30^@ with vertical, calculate the centripetal force acting on the stone. (g = 9.8 m/s^2)

A short bar magnet has magnetic moment 20 Am^2 . The axis of the magnet is in the magnetic meridian with the south pole pointing north. The horizontal component of earth's magnetic field at that place is 3 xx 10^-5 T. Find the point on the axis of the magnet at which the resultant magnetic field is zero, [such a point is called a neutral point].

A magnet makes 30 vibrations per minute at a place, where horizontal component of earth's field is 0.18G. At another place if it takes 1.6s to complete one vibration. What is the value of horizontal component of earth s field there? What is the magnetic moment if its moment of inertia is 10^-5 kg m^2 ?

Sonometer wire is kept under tension of 2kg wt . If resonating length of the wire is 18 cm in fundamental mode of vibration , find the frequency of vibration of the wire. (Linear density of the wire = 0.008 gram /cm, g = 9.8 m/s^2 )

A magnetic needle placed in uniform magnetic field has magnetic moment of 2xx10^-2 Am^2 , and moment of inertia of 7.2xx10^7 kgm^2 . It performs 10 complete oscillations in 6s. What is the magnitude of the magnetic field?

Two short bar magnets of length 1cm each have magnetic moments 1.20 Am^(2) and 1.00 Am^(2) respectively. They are placed on a horizontal table parallel to each other with their N poles pointing towards the south. They have a common magnetic equator and are separted by a distance of 20.0 cm . The value of the resultant horizontal magnetic induction at the mid - point O of the line joining their centres is close to (Horizontal component of earths magnetic induction is 3.6 xx 10.5 Wh//m^(2)