Question

Assertion(A): $\chi -T$ graph for a diamagnetic material is a straight line parallel to $T$ axis
Reason (R): This is because susceptibility of a diamagnetic material is not affected by temperature

• A. both A,R are true and R is the correct explanation of A
• B. both A,R are true and R is not correct explanation of A
• C. A is true, R is false
• D. A is false R is true

Answer 1

Answer: (A)

both A,R are true and R is the correct explanation of A

This problem is based on Magnetism.

$\bullet$ Magnetic Susceptibility is the tendency of a substance to get magnetised when placed in magnetic field. It is denoted by $\chi$ pronounced as $chi.$ It has no unit.

$\bullet$ Diamagnetic materials are those which are slightly repelled by a magnet. When placed in a magnetic field they get magnetised in a direction opposite to that of the field. Susceptibility $\chi$ of diamagnetic substances is negative.

$\bullet$ However, their susceptibility shows negligible change when heated or cooled. Their $\chi$ remains unchanged with change in temperature. Temperature is denoted by $T.$

Now look at the diagram.

It is a graph of susceptibility with respect to temperature for a diamagnetic material. Temperature is in Celcius.

The green line shows the change in $\chi$ with respect to $T.$

You can see that it is almost parallel to the $T$ axis.

Since$\chi$ is negative and $T$ is positive, the line is in the 4th quadrant.