Advertisements
Advertisements
प्रश्न
What happens to a ferromagnetic material when its temperature increases above curie temperature?
Advertisements
उत्तर
A ferromagnetic material is made up of small regions known as domains. The atomic magnetic moments of nearest-neighbour atoms interact strongly within each domain via exchange interaction, a quantum mechanical phenomenon, and align parallel to each other even in the absence of an external magnetic field. As a result, a domain is spontaneously magnetised to saturation.
Only up to a specific temperature does the material keep its domain structure. When heated, the increased thermal agitation opposes spontaneous domain magnetization. Finally, at a critical temperature known as the Curie point or Curie temperature, thermal agitation overcomes the exchange forces and maintains the atomic magnetic moments randomly oriented. As a result, the material becomes paramagnetic above the Curie point. The ferromagnetic to paramagnetic transition is a transition from order to disorder. The material becomes ferromagnetic again when cooled below the Curie point.
संबंधित प्रश्न
Distinguish between ‘paramagnetic’ and ‘ferromagnetic’ substances.
Show diagrammatically the behaviour of magnetic field lines in the presence of (i) paramagnetic and (ii) diamagnetic substances. How does one explain this distinguishing feature?
A meter gauge train is heading north with speed 54 km/hr in earth's magnetic field 3 x 10-4T. The e.m.f. induced across the axle joining the wheels is ..........
(a) 0.45 mV
(b) 4.5 mV
(c) 45 mV
(d) 450 m V
Which of the following substances are para-magnetic?
Bi, Al, Cu, Ca, Pb, Ni
The magnetic susceptibility of platinum is 0.0001. It's relative permeability is:
Answer the following question.
Write three points of differences between para-, dia- and ferromagnetic materials, giving one example for each.
Which of the following statements is correct for diamagnetic materials?
Choose the correct option:
A 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. Its period of oscillation is T′, the ratio of T′/T is ______.
For a paramagnetic substance, the magnetic susceptibility is ______.
The magnetic susceptibility of a paramagnetic material at - 73 °C is 0.0075. Its value at -173 °C will be ______.
Magnetic material can be easily magnetized if magnetic susceptibility is ______.
If a magnetic field is applied to a liquid in one arm of a narrow U-tube, the liquid level in that arm is lowered. The liquid in U-tube arm is ______.
Relative permittivity and permeability of a material are `epsilon_"r"` and `µ_"r"` respectively. Which of the following values of these quantities are allowed for a diamagnetic material?
There are three needles 'N1', 'N2' and 'N3' made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. When a magnet is brought close to them, then it will ____________.
The materials having negative magnetic susceptibility are ____________.
The product of magnetic susceptibility (`chi`) and absolute temperature (T) is constant for a ____________.
Which graph shows the variation of magnetic susceptibility (`chi`) with magnetizing field (H) for a paramagnetic substance?
Why is diamagnetism, in contrast, almost independent of temperature?
If a toroid uses bismuth for its core, will the field in the core be (slightly) greater or (slightly) less than when the core is empty?
Magnetic field lines are always nearly normal to the surface of a ferromagnet at every point. (This fact is analogous to the static electric field lines being normal to the surface of a conductor at every point.) Why?
A Rowland ring of mean radius 15 cm has 3500 turns of wire wound on a ferromagnetic core of relative permeability 800. What is the magnetic field B in the core for a magnetising current of 1.2 A?
Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond curie temperature, then it will show ______.
The given figure represents a material which is ______.
Assertion: A paramagnetic sample display greater magnetisation (for the same magnetic field) when cooled.
Reason: The magnetisation does not depend on temperature.
Two identical bar magnets are fixed with their centres at a distance d apart. A stationary charge Q is placed at P in between the gap of the two magnets at a distance D from the centre O as shown in the figure. The force on the charge Q is ______.
The magnetic susceptibility for diamagnetic materials is ______.
Earth's magnetic field analyses has a horizontal component except at:-
A hydrogen atom is paramagnetic. A hydrogen molecule is
For a diamagnetic material
Most of the substance show which of the magnetic property:-
If a charged particle at rest experience no electromagnetic force
According to the Atomic theory, on heating a magnet, the thermal energy of the elementary magnet ______
A paramagnetic sample shows a net magnetisation of 8 Am–1 when placed in an external magnetic field of 0.6 T at a temperature of 4 K. When the same sample is placed in an external magnetic field of 0.2 T at a temperature of 16 K, the magnetisation will be ______.
S is the surface of a lump of magnetic material.
- Lines of B are necessarily continuous across S.
- Some lines of B must be discontinuous across S.
- Lines of H are necessarily continuous across S.
- Lines of H cannot all be continuous across S.
A long solenoid has 1000 turns per metre and carries a current of 1 A. It has a soft iron core of µr = 1000. The core is heated beyond the Curie temperature, Tc.
- The H field in the solenoid is (nearly) unchanged but the B field decreases drastically.
- The H and B fields in the solenoid are nearly unchanged.
- The magnetisation in the core reverses direction.
- The magnetisation in the core diminishes by a factor of about 108.
A uniform magnetic field gets modified as shown in figure when two specimens A and B are placed in it.
 |
 |
| (a) | (b) |
- Identify the specimen A and B.
- How is the magnetic susceptibility of specimen A different from that of specimen B?
An ammeter of resistance R gives a full-scale deflection when a current of 2 A passes through it. If it is measured with a maximum current of 10 A, the required shunt is ______.
- Assertion (A): Diamagnetic substances exhibit magnetism.
- Reason (R): Diamagnetic materials do not have a permanent magnetic dipole moment.
Which of the following has a permeability less than that of free space?
The relative magnetic permeability of a substance X is slightly less than unity and that of substance Y is slightly more than unity, then ______.
Explain ferromagnetism on the basis of the domain theory.
Explain the meaning of the following statement:
Curie temperature for soft iron is 770°C.
Magnetic susceptibility of a diamagnetic substance ______.
Match List-I with List-II.
| List-I (Material) | List-II (Susceptibility) | ||
| A. | Diamagnetic | I. | χ = 0 |
| B. | Ferromagnetic | II. | 0 > χ ≥ −1 |
| C. | Paramagnetic | III. | χ >> 1 |
| D. | Non-magnetic | IV. | 0 < χ < ε |
Choose the correct answer from the options given below:
