Tag: magnetism and matter

Questions Related to magnetism and matter

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

Show answer
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

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

Show answer
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

Show answer
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

Susceptibility is large and positive 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

Show answer
Correct Option: C
Explanation:

Diamagnetic          Paramagnetic             ferromagnetic
-1 $\leq$ $\chi$ < 0            0 < $\chi$ < $\varepsilon$                 $\chi$ >>1
$\chi $$=$magnetic susceptibility

The core of electromagnet is made of soft iron, because
a) susceptibility of soft iron is very high
b) coercivity of soft iron is very low

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

  1. only a is correct

  2. only b is correct

  3. both a and b are correct

  4. both a and b are wrong

Show answer
Correct Option: C
Explanation:
Because the suceptibility of the soft iron is very high. and its coercivity is very low,it is very less corrosive. 
$\chi$ >> 1 (Because it is a ferromagnetic substance.)

The value of susceptibility for super conductor is

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

  1. 0

  2. $\infty $

  3. +1

  4. -1

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Correct Option: D
Explanation:

-1, Because superconductor are perfect diamagnetic substances.

Susceptibility is positive and large for a

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

  1. paramagnetic substance

  2. ferromagntic substance

  3. diamagnetic substance

  4. non magnetic substance

Show answer
Correct Option: B
Explanation:

For ferromagnetic substances, $\chi _m$ is large and positive.