Question 81:
easy31. Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show: (2007)
When a ferromagnetic substance like nickel is heated beyond its Curie temperature ($T_C$), domain alignment is disrupted by thermal energy, and it behaves as a paramagnetic substance.
Question 82:
easy32. Above Curie temperature: (2006)
At temperatures higher than the Curie temperature, spontaneous magnetization in ferromagnetic materials vanishes and the substance transforms into a paramagnetic material obeying Curie-Weiss law.
Question 83:
easy33. According to Curie’s law, the magnetic susceptibility of a substance at an absolute temperature T is proportional to: (2003)
According to Curie's law for paramagnetic substances, magnetic susceptibility is inversely proportional to absolute temperature $T$, i.e., $\chi = \frac{C}{T}$, or $\chi \propto 1/T$.
Question 84:
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 diamagnetic rod moves out of the magnetic field, it modifies the magnetic flux through the electromagnet. To maintain the magnetic field and current against the back emf, the current source does extra work, which provides the gained gravitational potential energy.
Question 85:
easy21. The magnetic susceptibility is negative for: (2016 – I)
Magnetic susceptibility $\chi$ is defined as $I/H$. Diamagnetic substances develop magnetization in a direction opposite to the applied magnetic field, so their magnetic susceptibility is negative.
Question 86:
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 are feebly repelled (A), paramagnetic materials are feebly attracted (B), ferromagnetic materials are strongly attracted (C), and non-magnetic materials remain unaffected (D). Therefore, B is a paramagnetic material.
Question 87:
easy23. The magnetic moment of a diamagnetic atom is: (2010 Mains)
In diamagnetic materials, all electrons are paired, and the magnetic moments of paired electrons cancel each other out completely in every atom. Hence, each diamagnetic atom has zero net magnetic dipole moment.
Question 88:
easy24. If a diamagnetic substance is brought near the north or the south pole of a bar magnet, it is: (2009)
Diamagnetic materials tend to move from regions of stronger magnetic fields to weaker magnetic fields. Since the magnetic field is strongest near both poles, the substance is repelled by both the north and south poles.