Question 151:
easy26. Diamagnetic material in a magnetic field moves: (2003)
Diamagnetic materials get magnetized in the opposite direction to the applied external magnetic field. Because of this repulsion, they experience a net force moving them from the stronger region to the weaker region of the field.
Question 152:
easy27. Among which the magnetic susceptibility does not depend on the temperature: (2001)
According to Curie's law, the susceptibility of paramagnetic and ferromagnetic materials varies inversely with temperature. However, the magnetic susceptibility of diamagnetic materials is practically independent of temperature.
Question 153:
easy28. For protecting a magnetic needle it should be placed: (1998)
Soft iron is a ferromagnetic material with high permeability. When an iron box is placed in an external magnetic field, most of the magnetic field lines pass through the walls of the box, shielding the inside space.
Question 154:
easy29. Electromagnets are made of soft iron because soft iron has: (2010 Pre)
Electromagnets require a material that gets magnetized easily and quickly loses its magnetism when the current is turned off. Soft iron is ideal because it has low retentivity and low coercive force.
Question 155:
easy30. Curie temperature is the temperature above which: (2008)
At the Curie temperature, the thermal agitation overcomes the exchange interaction between atomic dipoles that align them. Above this temperature, the ferromagnetic material loses its spontaneous magnetization and behaves as a paramagnetic material.
Question 156:
easy31. Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show: (2007)
Nickel is a ferromagnetic material. When heated above its Curie temperature, the magnetic domain structure breaks down due to thermal agitation, transforming it into a paramagnetic substance.
Question 157:
easy32. Above Curie temperature: (2006)
The Curie temperature is the critical temperature point at which a material's intrinsic permanent magnetic moments change state. Heating a ferromagnetic substance above this point turns it into a paramagnetic substance.
Question 158:
easy33. According to Curie’s law, the magnetic susceptibility of a substance at an absolute temperature $T$ is proportional to: (2003)
Curie's law states that the magnetic susceptibility ($\chi$) of a paramagnetic substance is inversely proportional to its absolute temperature ($T$). Therefore, $\chi \propto 1/T$.
Question 159:
easy20. A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from: (2018)
When the rod is pushed up, work is done against gravity. To maintain the steady magnetic field against this change, the current source (battery) must do work. Thus, the energy ultimately comes from the current source.
Question 160:
easy21. The magnetic susceptibility is negative for: (2016-I)
Magnetic susceptibility is negative for diamagnetic materials because they develop an induced magnetization in the direction opposite to the applied magnetic field. It is positive for paramagnetic and ferromagnetic materials.