Question 1

How do paramagnetic and diamagnetic substances respond to a magnetic field?

Accepted Answer

Paramagnetic substances are weakly attracted because their magnetic moments align weakly with the applied field. Diamagnetic substances are weakly repelled because an induced magnetic moment develops opposite to the field. Removing the external field removes these weak responses.

Question 2

What is magnetic hysteresis and what does its loop area represent?

Accepted Answer

Hysteresis is the path dependence of the magnetic response during a cycle of changing applied field. The area enclosed by the B-H loop gives the hysteresis energy loss per unit volume of material for one magnetisation cycle.

Question 3

What are remanence and coercivity?

Accepted Answer

Remanence B_r is the residual magnetic induction remaining when H returns to zero; the corresponding quantity for magnetisation is M_r. Coercivity H_c is the reverse applied field required to reduce B back to zero.

Question 4

What happens to a ferromagnetic material above its Curie temperature?

Accepted Answer

Above its Curie temperature, ferromagnetic ordering disappears and the material becomes paramagnetic. The transition marks the temperature beyond which the material no longer retains its strong ferromagnetic domain alignment.

Question 5

Is the slope of a B-H graph directly equal to susceptibility?

Accepted Answer

For a linear material, susceptibility is defined by χ = M/H. In SI units B = μ0(H + M), so the slope of B against H is μ0(1 + χ), or 1 + χ when B/μ0 is plotted against H.

Magnetic Materials: Domains, Hysteresis Loop and Susceptibility

About this lab

Practice