After the main questions now we are to take topic which are so called not very important.
Here we should understand the series and parallel connections of cells and their equivalent emf and equivalent resistances.
In second video we are taking some of the IMPORTANT conceptual questions pertaining the change in BALANCING LENGTH of potentiometer
this will even make you understand the concept of potentiometer MORE strongly.
Important way is to try to solve the questions first of all your self than you see the solution