Question 51:
easy13. Due to earth’s magnetic field, the charged cosmic rays particles (1997)
At the equator, charged particles travel perpendicular to the Earth's magnetic field lines and experience maximum deflecting force. Thus, they need greater kinetic energy to penetrate the field and reach the equator compared to the poles.
Question 52:
easy14. A vibration magnetometer placed in magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of $2$ sec in earth’s horizontal magnetic field of $24$ microtesla. When a horizontal field of $18$ microtesla is produced opposite to the earth’s field by placing a current carrying wire, the new time period of magnet will be: (2010 Pre)
Initial field $B_1 = 24$ $\mu$T, $T_1 = 2$ s. Net new field $B_2 = 24 - 18 = 6$ $\mu$T.
Since $T \propto \frac{1}{\sqrt{B}}$, we have $\frac{T_2}{T_1} = \sqrt{\frac{B_1}{B_2}} = \sqrt{\frac{24}{6}} = \sqrt{4} = 2$. Therefore, $T_2 = 2 \times 2 = 4$ s.
Question 53:
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 54:
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 55:
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 56:
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 57:
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.
Question 58:
easy22. There are four light weight rod samples A, B, C, D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted:
(i) A is feebly repelled
(ii) B is feebly attracted
(iii) C is strongly attracted
(iv) D remains unaffected
Which one of the following is true? (2011 Pre)
Diamagnetic materials (A) are feebly repelled. Paramagnetic materials (B) are feebly attracted. Ferromagnetic materials (C) are strongly attracted. Non-magnetic materials (D) remain unaffected. Hence, B is paramagnetic.
Question 59:
easy23. The magnetic moment of a diamagnetic atom is: (2010 Mains)
In diamagnetic materials, electrons occur in pairs with opposite spins and their orbital motions cancel each other out. Thus, their individual magnetic moments cancel, resulting in a net magnetic moment equal to zero for the atom.
Question 60:
easy24. If a diamagnetic substance is brought near the north or the south pole of a bar magnet, it is: (2009)
Diamagnetic substances always move from stronger parts to weaker parts of a non-uniform magnetic field. Therefore, they are repelled by both the north and south poles of a bar magnet.