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

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

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

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

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

  4. ${ \mu } _{ r }<1,{ \chi } _{ m }>0$
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

Susceptibility is large and positive for

  1. para magnetic

  2. diamagnetic

  3. ferro magnetic

  4. electromagnetic
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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

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

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

  1. only a is correct

  2. only b is correct

  3. both a and b are correct

  4. both a and b are wrong
Reveal answer Fill a bubble to check yourself
C Correct answer
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.)
Multiple choice physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

The magnetic materials having negative magnetic susceptibility are

  1. non-magnetic

  2. para magnetic

  3. dia magnetic

  4. ferro magnetic
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Magnetic susceptibility is a dimensionless proportionality constant that indicates the degree of magnetisation of a material in response to an applied magnetic field.

Substances such as copper, iron have negative susceptibility as these substances are diamagnetic substances.
Substances with negative susceptibility signifies that they are repelled by magnets.

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

Which of the following group is diamagnetic?

  1. Copper, hydrogen, silver

  2. Copper, hydrogen, argon

  3. Hydrogen, oxygen, argon

  4. Copper, silver, oxygen
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Diamagnetic substances are those which are freebly repelled by the magnetic field.
$\therefore$ Copper, Hydrogen, Silver are diamagnetic as their atoms have net magnetic dipole moment zero.