а. Where is the electric field stronger, point A or point B? Explain using physical reasoning. b. If a proton is fired from point B toward point C, will its speed at C be greater than, less than, or the same as B? Explain using physical reasoning.

Electric Field

The electric field is a region in space around a charge or a system of charges such that if a test charge is brought into the region, it will experience a force due to the source charges.

The magnitude of the electric field strength due to a point charge $q$ at a distance $r$ from it is

$E=\frac{1}{4\pi {\epsilon }_o}\frac{q}{r^2}$

Electric Potential 

The electric potential at a point is the amount of work done by an external agency in bringing a unit positive charge from infinity to that point under the influence of the electric field produced by other charges.

The electric potential due to a point charge $q$ at a distance $r$ from it is

$V=\frac{1}{4\pi {\epsilon }_o}\frac{q}{r}$

If we have two equipotential surfaces such that the potential difference between the equipotential surfaces is $dV$ and the distance between them is $dr$, the electric field between the two surfaces is 

$E=-\frac{dV}{dr}$

Here $\frac{dV}{dr}$ is known as the potential gradient.