1. Explain how the potential difference (voltage) in a battery is similar to a staircase. ?
The potential difference across each cell is like going up (or down) one step on the staircase.
A battery is a set of individual cells in series.
Each cell has a potential difference (voltage) across it when charged. Voltage is proportional to the potential energy stored in the battery (Volts x Amp-hours = energy)
If the cells are the same type and at the same state of charge, as they should be in a battery of cells, then their voltages will be the same.
Measuring from one end of the battery, the potential difference changes in steps of one cell voltage per cell.
This is similar to the way the potential energy of a mass changes as it moves from one step to another on a staircase