Explain electric field and its source as well as magnetic field and its source.

(N/A) The source of an electric field is an electric charge.
If a charge $Q$ is static,the electric field produced around it is given by:
$\overrightarrow{E} = \frac{k Q}{r^{2}} \hat{r} = \frac{Q}{4 \pi \epsilon_{0} r^{2}} \hat{r}$
where $\hat{r}$ is the unit vector of the position vector $\vec{r}$ and $\overrightarrow{E}$ is the electric field vector.
The force on a charged particle $q$ in an electric field is given by:
$\overrightarrow{F} = q \overrightarrow{E} = \frac{k Q q}{r^{2}} \hat{r}$
Electric fields convey energy and momentum and propagate at a finite speed. The field at any point can be due to one or more charges,where the total field is the vector sum of individual fields (Principle of Superposition).
Static charges produce only an electric field. Moving charges (currents) produce both an electric field and a magnetic field,denoted by $\overrightarrow{B}(\vec{r})$.
Magnetic field is a vector quantity defined at each point in space and can vary with time. The magnetic field of multiple sources is the vector sum of the magnetic fields of each individual source,obeying the principle of superposition.