How to obtain Potential Difference between two points in a Electric Field region , if E is given

How is potential difference between two points expressed?

Potential difference between the points B and E of the circuit is -

Potential difference between the points P and Q in the electric circuit shown is

What is the potential difference between two points in the electric field? Name its SI unit.

The device used to measure potential difference between two points in an electric circuit is "________" .

The potential difference between the points A and B in the given circuit is