Magnetism. Diamagnetics. Paramagentics. Ferromagnetics

Question 1

It is observed that a frog placed in a strong gradient of magnetic field
levitates. Explain the origin of this effect.

Answer 1

The effect is caused by diamagentism
ALL materials are diamagnetic M= χB
Diamagnetic materials have small negative values of the
susceptibility χ.
The magnetic force F is opposite to the gravity force mg
The magnetic field decreases with z(direction)
The magnetization of the frog will oppose an applied magnetic field and z(direction)
This repels the frog
If B is strong enough the repelling force will be able to match gravity causing the frog to levitate

Question 2

What is the energy U of a magnetic dipole in a

constant magnetic field B?

Answer 2

U =-μ ·B

Question 3

What is the energy difference
between a magnetic dipole oriented parallel and antiparallel to the
the direction of a magnetic

Answer 3

Parallel
U =-μ ·B
Antiparallel
U =-μ ·B

Energy difference

ΔU =-Δμ ·B

Question 4

Use Hund’s rules to write down the configuration of electrons in the unfilled
electronic shells and thereby calculate L, S, and J for both ions.

Answer 4

Step 1: Add electron spins to give maximum value of S (rule 2)

Step 2: Add orbital momenta to give maximum L (rule 3)

Step 3, J = L ± S. As shell is less than half filled, we must haveJ = L - S