$(10)$ Why is a course like this on electromagnetism and not just on electricity or magnetism alone. Give specific course$-$content examples to support your answer.

$(40)$ A double A $($AA$)$ battery has a voltage of $1\mathrm{.}5$ V $.$ A car battery has a voltage of $12$ V $.$ In spite of this, we cannot use a relatively small number of AA batteries to start a car. The issue is the internal resistance of the batteries. Recall that this internal resistance acts as if it is in series with the EMF of the battery. For a AA battery the internal resistance is around $0\mathrm{.}1$ and for the car battery it is one tenth of that value. How many AA batteries would it therefore take to replace a car battery such that the combination of AA batteries has the same internal resistance and terminal voltage as the car battery?