Advertisements
Advertisements
Question
A paramagnetic gas has 2.0 × 1026 atoms/m with atomic magnetic dipole moment of 1.5 × 10−23 A m2 each. The gas is at 27°C.
- Find the maximum magnetization intensity of this sample.
- If the gas in this problem is kept in a uniform magnetic field of 3 T, is it possible to achieve saturation magnetization? Why?
Advertisements
Solution
Data: `"N"/"V" = 2.0 xx 10^26` atoms/m3,
µ = 1.5 × 10-23 Am2, T = 27 + 273 = 300 K, B = 3 T, kB = 1.38 × 10-23 J/K, 1 eV = 1.6 × 10-19 J
(a) The maximum magnetization of the material,
`"M"_"z" = "N"/"V" mu = (2.0 xx 10^26)(1.5 xx 10^-23)`
= 3 × 103 A/m
(b) The maximum orientation energy per atom is
`upsilon_"max" = - mu"B" cos 180^circ = mu"B"`
`= (1.5 xx 10^-23)(3) = (4.5 xx 10^-23)/(1.6 xx 10^-19)`
= 2.8 × 10-4 eV
The average thermal energy of each atom,
E = `3/2 "k"_"B" "T"`
where kB is the Botzmann constant.
∴ E = 1.5(1.38 × 10-23)(300)
= 6.21 × 10-21 J = `(6.21 xx 10^-21)/(1.6 xx 10^-19)`
= 3.9 × 10-2 eV
Since the thermal energy of randomization is about two orders of magnitude greater than the magnetic potential energy of orientation, saturation magnetization will not be achieved at 300 K.
APPEARS IN
RELATED QUESTIONS
Give any ‘two’ points of differences between diamagnetic and ferromagnetic substances.
Out of the two magnetic materials, 'A' has relative permeability slightly greater than unity while 'B' has less than unity. Identify the nature of the materials 'A' and 'B'. Will their susceptibilities be positive or negative?
The susceptibility of a magnetic material is 0·9853. Identify the type of magnetic material. Draw the modification of the field pattern on keeping a piece of this material in a uniform magnetic field.
Answer the following question.
Write three points of differences between para-, dia- and ferromagnetic materials, giving one example for each.
Identify the following magnetic materials :
Choose the correct option:
A magnetising field of 360 Am−1 produces a magnetic flux density (B) = 0.6T in a ferromagnetic material. What is its permeability in Tm A−1?
A rod of magnetic material of cross-section 0.25 cm2 is placed in a magnetizing field of intensity 4000 A/m-1. The magnetic flux passing through the rod is 25 × 10-6 Wb. Find out
(a) relative permeability
(b) magnetic susceptibility and
(c) magnetisation of the rod.
Two identical bar magnets each of magnetic moment M, separated by some distance are kept perpendicular to each other. The magnetic induction at a point at the same distance d from the centre of magnets, is (µ0 = permeability of free space)
The magnetic susceptibility of a paramagnetic material at - 73 °C is 0.0075. Its value at -173 °C will be ______.
Magnetization of the sample 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?
The materials having negative magnetic susceptibility are ____________.
Above the curie temperature the susceptibility of ferromagnetic substance varies ____________.
A sphere of gold when brought towards a powerful magnet experiences ____________.
A small quantity of paramagnetic liquid is taken in a watch - glass and kept on two dissimilar magnetic poles. The liquid ____________.
A domain in a ferromagnetic substance is in the form of a cube of side length 1 µm. If it contains 6 x 1010 atoms and each atomic dipole has a dipole moment of 7 x 10-24 Am2, then magnetization of the domain is ____________.
The earth’s field departs from its dipole shape substantially at large distances (greater than about 30,000 km). What agencies may be responsible for this distortion?
Which graph shows the variation of magnetic susceptibility (`chi`) with magnetizing field (H) for a paramagnetic substance?
Why does a paramagnetic sample display greater magnetisation (for the same magnetising field) when cooled?
Why is diamagnetism, in contrast, almost independent of temperature?
Is the permeability of a ferromagnetic material independent of the magnetic field? If not, is it more for lower or higher fields?
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?
Explain qualitatively on the basis of domain picture the irreversibility in the magnetisation curve of a ferromagnet.
A certain region of space is to be shielded from magnetic fields. Suggest a method.
The magnetic susceptibility is negative for ______.
Metals getting magnetised by orientation of atomic magnetic moments in external magnetic field are called ______.
Which of the following property shows the property of ferromagnetic substances?
A hydrogen atom is paramagnetic. A hydrogen molecule is
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 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.
Explain quantitatively the order of magnitude difference between the diamagnetic susceptibility of N2 (~5 × 10–9) (at STP) and Cu (~10–5).
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 cannot modify an external magnetic field as shown in the figure?
State the dimensions of magnetization.
Magnetic susceptibility of a diamagnetic substance ______.
