Many times in the use and calculation of electric and magnetic fields, the approach used first computes an associated potential: the electric potential, φ φ , for the electric field, and the magnetic vector potential, A, for the magnetic field. The electric potential is a scalar field, while the magnetic potential is a vector field. This is why sometimes the electric potential is called the scalar potential and the magnetic potential is called the vector potential. These potentials can be used to find their associated fields as follows: E = − − ∇ ∇ φ φ − − ∂ ∂ A ∂ ∂ t B = ∇ ∇ × × A