Finding the electric and magnetic fields from a scalar potential?

[bagherihan]

E = - grad*phi - 1/c (dA/dt).
phi is the scalar potential, and is given. How do I calculate the vector potential = A ?
Is it A = (v/c) * phi ? If it is, then where is this equation coming from?
Thank you.

 

[jtbell]

In order to find the magnetic vector potential $\vec A$ you need to know either the magnetic field $\vec B$ or the current density $\vec J$.

http://farside.ph.utexas.edu/teaching/em/lectures/node38.html

 

[BruceW]

yeah, in any case, it is not possible to calculate the vector potential by only using the scalar potential and nothing else.