Tag: magnetic materials

Questions Related to magnetic materials

Mark the correct set of ferromagnetic substances,

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. iron, cobalt and nickel

  2. iron, copper and lead

  3. silicon, bismuth and nickel

  4. aluminium, sodium and copper.

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Correct Option: A
Explanation:

Iron, cobalt and nickel are the examples of ferromagnetic material.

Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show the

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. anti ferromagnetism

  2. no magnetic property

  3. diamagnetism

  4. paramagnetism

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Correct Option: D
Explanation:

Above Curie temperature, ferromagnetic material become paramagnetic.

Assertion : When diamagnetic material is placed in a non-uniform magnetic field, it tends to move from stronger to the weaker part of the magnetic field.
Reason : Diamagnetic materials possess strong magnetism.

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. If both assertion and reason are true and reason is the correct explanation of assertion.

  2. If both assertion and reason are true and reason is not the correct explanation of assertion.

  3. If assertion is true but reason is false.

  4. If both assertion and reason are false.

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Correct Option: C
Explanation:

Electrons is an atom orbiting around nucleus possess orbital angular momentum. These orbiting electrons are equivalent to current-carrying loop and thus possess orbital magnetic moment. Diamagnetic substances are the ones in which resultant magnetic moment in an atom is zero. When magnetic field is applied, those electrons having orbital magnetic moment in the same direction slow down and those in the opposite direction speed up. Thus, the substance develops a net magnetic moment in direction opposite to that of the applied field.

Assertion : At high temperature, a ferromagnet becomes a paramagnet.
Reason : The ferromagnetic property depends on temperature.

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. If both assertion and reason are true and reason is the correct explanation of assertion.

  2. If both assertion and reason are true and reason is not the correct explanation of assertion.

  3. If assertion is true but reason is false.

  4. If both assertion and reason are false.

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Correct Option: A
Explanation:

At enough high temperature, a ferromagnet become a paramagnet. The domain structure disintegrates with temperature.

Assertion : The product of magnetic susceptibility and absolute temperature for a paramagnetic substance is constant.
Reason : Susceptibility is positive but very small for paramagnetic substance.

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. If both assertion and reason are true and reason is the correct explanation of assertion.

  2. If both assertion and reason are true and reason is not the correct explanation of assertion.

  3. If assertion is true but reason is false.

  4. If both assertion and reason are false

Show answer
Correct Option: B
Explanation:

The susceptibility of a paramagnetic substance is inversely proportional to absolute temperature.
$X \propto \frac{1}{T}$
Hence $XT = constant$
Also for paramagnetic substances the susceptibility is positive and very small.

If a magnetic material is having magnetic susceptibility $(\chi)=-1$, then the relative magnetic permeability $(\mu _r)$ and type of magnetic material is?

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. $0$, diamagnetic

  2. $2$, ferromagnetic

  3. $1$, paramagnetic

  4. $-1$, diamagnetic

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Correct Option: A
Explanation:

Here, $\chi =-1$
then $\mu _r=1+\chi \Rightarrow \mu _r=1+(-1)=I-1=0$
Since, magnetic susceptibility of given material is less than one. Hence, the given magnetic material is a diamagnetic material.

A domain in ferromagnetic iron is in the form of a cube of side length $2$ $\mu m$ then the number of iron atoms in the domain are (Molecular mass of iron $=55$g $mol^{-1}$ and density $=7.92$g $cm^{-3}$)

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. $6.92\times 10^{12}$ atoms

  2. $6.92\times 10^{11}$ atoms

  3. $6.92\times 10^{10}$ atoms

  4. $6.92\times 10^{13}$ atoms

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Correct Option: B
Explanation:

The volume of the cubic domain
$V=(2\mu m)^3=(2\times 10^{-6}m)^3$
$=8\times 10^{-18}m^3=8\times 10^{-12}cm^3$
and mass $=$volume $\times$ density
$=8\times 10^{-12}cm^3\times 7.9g cm^{-3}$
$=63.2\times 10^{-12}$g
Now the Avagadro number $(6.023\times 10^{23})$ of iron atoms have a mass of $55$g. Hence the number of atoms in the domain are.
$N=\dfrac{63.2\times 10^{-12}\times 6.023\times 10^{23}}{55}=6.92\times 10^{11}$ atoms.

Which of the following is true regarding dimagnetic substances (symbols have their usual meaning)?

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. ${ \mu } _{ r }>1,{ \chi } _{ m }>1$

  2. ${ \mu } _{ r }>1,{ \chi } _{ m }<1$

  3. ${ \mu } _{ r }<1,{ \chi } _{ m }<0$

  4. ${ \mu } _{ r }<1,{ \chi } _{ m }>0$

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Correct Option: C
Explanation:

Diamagnetic substances induce magnetic field in the direction opposite to an external applied magnetic field and thus are repelled by external applied magnetic field.

Magnetic susceptibility of these substances is very small and negative    i.e    $\chi _m  < 0$ 
For example:
For silicon, $\chi _m =  -4.2 \times 10^{-6}$
From the equation, $\mu _r = 1+ \chi _m$
Thus, $\chi _m<0$ $\implies  \mu _r  <1$    
Hence, such materials have magnetic permeability less than unity.

Susceptibility is small and negative for

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. para magnetic

  2. diamagnetic

  3. ferro magnetic

  4. electromagnetic

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Correct Option: B
Explanation:

diamagnetic
$-1 \leq x < 0$
$\chi =susceptibility$

Susceptibility is small and positive for

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. para magnetic only

  2. diamagnetic only

  3. ferro magnetic only

  4. Both 1 & 3

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Correct Option: A
Explanation:

Paramagnetic material $0< \chi < \varepsilon $
$\varepsilon $ it small, positive and less than one.
$\chi $ is suscepticity