# Introduction to Mathematical Physics/Electromagnetism/Exercises

**Exercice:**

exoeqhelmoltz

Assume constitutive relations to be:

where represents temporal convolution\index{convolution} (value of field at time S depends on values of at preceeding times) and

Show that in harmonical regime () and without
any charges field verifies *Helmholtz equation* :

Give the expression of .

**Exercice:**

Show (see ([#References

**Exercice:**

Proove charge conservation equation eqconsdelacharge from Maxwell equations.

**Exercice:**

Give the expression of electrical potential created by quadripole .

**Exercice:**

Show from the expression of magnetic energy that force acting on a point charge with velocity is: