Question 1
In the water tank analogy, what corresponds to the potential difference in an electric circuit?
The right answer is the one marked above.
The pressure difference between the two ends of the pipe. Raising the tank increases the pressure difference and the water flows faster. The electric source does the same thing with an electric pressure difference.
The point of the analogy is that a flow needs a difference, not just a supply. Water does not run because there is water; it runs because one end is higher.