Magnetic Properties of Matter

A paramagnetic sample shows a net magnetisation of 6 A/m when it is placed in an external
magnetic field of 0.4 T at a temperature of 4 K. When the sample is placed in an external magnetic
field of 0.3 T at a temperature of 24 K, then the m...

A perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a
paramagnetic substance. The whole system is placed in a uniform magnetic field \(\overrightarrow B\)
. Then the field
inside the paramagnetic...

Magnetic materials used for making permanent
magnets (P) and magnets in a transformer (T)
have different properties of the following,
which property best matches for the type of
magnet required?

A bar magnet is demagnetized by inserting it inside a solenoid of length 0.2 m, 100 turns, and carrying a current of 5.2 A. The corecivity of the bar magnet is :

Two magnetic dipoles X and Y are placed at
a separation d, with their axes perpendicular to
each other. The dipole moment of Y is twice
that of X. A particle of charge q is passing,
through their midpoint P, at angle q = 45° with
the horizo...

A paramagnetic material has 1028 atoms/m3. Its magnetic susceptibility at temperature 350 K is 2.8 \(\times\) 10–4. Its susceptibility at 300 K is :

A magnetic compass needle oscillates 30 times per minute at a place where the dip is 45o, and 40 times per
minute where the dip is 30o. If B1 and B2 are respectively the total magnetic field due to the earth at the two
places, then the rati...

A paramagnetic substance in the form of a cube with sides 1 cm has a magnetic dipole moment of 20 \(\times\) 10–6 J/ T when a magnetic intensity of 60 \(\times\) 103 A/m is applied. Its magnetic susceptibility is

A magnet of total magnetic moment 10-2 \({\widehat i}\) A-m2 is placed in a time varying magnetic field, B\({\widehat i}\) (cos \(\omega t\)) where B = 1 Tesla and \(\omega\) = 0.125 rad/s. The work done for reversing the direction of th...

At some location on earth, the horizontal component of earth’s magnetic field is 18 × 10–6 T. At this location, magnetic needle of length 0.12 m and pole strength 1.8 Am is suspended from its mid-point using a thread, it makes 45o angle wit...

The \(B\)-\(H\) curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solended with \(1000\) turns/cm. The current that should be passed in the solended to demagnetise the ferromagnet completely is :

A magnetic needle of magnetic moment 6.7 \(\times\) 10-2 A m2 and moment of inertia 7.5 \(\times\) 10-6 kg m2 is
performing simple harmonic oscillations in a magnetic field of 0.01 T. Time taken for 10 complete oscillations is:

A fighter plane of length 20 m, wing span (distance from tip of one wing to the tip of the other wing) of 15 m and height 5 m is flying towards east over Delhi. Its speed is 240 ms−1. The earth’s magnetic field over Delhi is 5 \(\times\)1...

Hysteresis loops for two magnetic materials \(A\) and \(B\) are given below :

These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then it is proper to use :

An example of a perfect diamagnet is a superconductor. This implies that when a superconductor is put in a magnetic field of intensity B, the magnetic field Bs inside the superconductor will be such that :

The coercivity of a small magnet where the ferromagnet gets demagnetized is \(3 \times {10^3}\,A{m^{ - 1}}.\) The current required to be passed in a solenoid of length \(10\) \(cm\) and number of turns \(100,\) so that the magnet gets demag...

Two short bar magnets of length \(1\) \(cm\) each have magnetic moments \(1.20\) \(A{m^2}\) and \(1.00\) \(A{m^2}\) respectively. They are placed on a horizontal table parallel to each other with their \(N\) poles pointing towards the Sout...

Relative permittivity and permeability of a material \({\varepsilon _r}\) and \({\mu _r},\) respectively. Which of the following values of these quantities are allowed for a diamagnetic material?

Needles \({N_1}\), \({N_2}\) and \({N_3}\) are made of ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will

A magnetic needle is kept in a non-uniform magnetic field. It experiences :

The length of a magnet is large compared to its width and breadth. The time period of its oscillation in a vibration magnetometer is \(2s.\) The magnet is cut along its length into three equal parts and these parts are then placed on each o...

Curie temperature is the temperature above which

The materials suitable for making electromagnets should have

A magnetic needle lying parallel to a magnetic field requires \(W\) units of work to turn it through \({60^ \circ }.\) The torque needed to maintain the needle in this position will be :

A thin rectangular magnet suspended freely has a period of oscillation equal to \(T.\) Now it is broken into two equal halves (each having half of the original length) and one piece is made to oscillate freely in the same field. If its peri...

The magnetic lines of force inside a bar magnet