Magnetic Properties Of Materials - Practice Questions & MCQ

Depending on the magnetic properties, the magnetic materials are classified as

• Diamagnetic substance 
• Paramagnetic substance 
• Ferromagnetic substance

Diamagnetic substance-

The substance which is feebly magnetized in a direction opposite to that of the magnetizing field in which those are placed.

bismuth, copper, lead, silicon, etc are diamagnetic substances.

And for diamagnetic substances

$\begin{gathered}\chi<0 \\ 0 \leq \mu_r<1 \\ \mu<\mu_0\end{gathered}$

Magnetization(M) Vs The magnetic intensity (H) curve-

Magnetic moment (m) for diamagnetic substances is Very low or nearly 0.

The cause of magnetism for Diamagnetic substances is the Orbital motion of electrons.

Diamagnetic substances are those which have a tendency to move from stronger to the weaker part of the external magnetic field.

 The magnetic field lines are expelled by these substances.

Behavior in a non-uniform magnetic field In diamagnetic substance-

I.e These are repelled in an external magnetic field.  

Paramagnetic substances-

Paramagnetic substances are those which get weakly magnetized when placed in an external magnetic field.

And for Paramagnetic substances

$\begin{gathered}0<\chi<\varepsilon \\ 1<\mu_r<1+\varepsilon \\ \mu>\mu_0\end{gathered}$

Magnetization(M) Vs The magnetic intensity (H) curve-

They have a tendency to move from a region of the weak magnetic field to a strong magnetic field.

i.e., they get weakly attracted to a magnet.

Cause of magnetism-Spin motion of electrons

Magnetic moment (m) for Paramagnetic substances is Very low.

Behavior in a non-uniform magnetic field In Paramagnetic substance-

i.e These are feebly attracted in an external magnetic field.

Ferromagnetic substances-

The substance which is strongly magnetized in the direction of the magnetizing field in which they are placed.

Iron, cobalt, nickel, gadolinium, and the number of alloys are ferromagnetic in nature.

And for ferromagnetic substances

$\begin{aligned} & \chi \gg>1 \\ & \mu_r \gg>1 \\ & \mu \gg>\mu_0\end{aligned}$

Magnetization(M) Vs The magnetic intensity (H) curve-

The cause of magnetism is the Formation of domains.

Magnetic moment (m) for ferromagnetic substances is Very high.

They have strong tendency to move from a region of weak magnetic field to strong magnetic field.

Magnetic field lines tend to crowd into a ferromagnetic substance.

Behavior in a non-uniform magnetic field In ferromagnetic substance-

I.e These are strongly attracted in an external magnetic field

• Curie Temperature or Curie Point-

It is the temperature above which increasing the temperature the susceptibility of ferromagnetic materials decreases.

i.e At a temperature above the Curie Point a ferromagnetic becomes an ordinary Paramagnetic

It is denoted by T_c.

Curie-Weiss curve-

From the above curve, we can say that (For $\left.\mathrm{T}>\mathrm{T}_{\mathrm{c}}\right) \quad \chi_{\mathrm{m}} \propto \frac{1}{\mathrm{~T}-\mathrm{T}_{\mathrm{c}}}$ or $\chi_{\mathrm{m}}=\frac{\mathrm{C}}{\mathrm{T}-\mathrm{T}_{\mathrm{c}}}$ where C is some constant.