By our sign conventions, if a battery is traversed in the actual direction of the current in it, what can you say about the sign of the change in electric potential (the battery’s terminal voltage)?
In order to determine the sign of the change in electric potential or the battery's terminal voltage when traversing a battery in the actual direction of the current, we need to understand the sign conventions commonly used.
By convention, when we consider the flow of positive charge, current is defined as the movement of positive charges. However, in reality, electrons (negative charges) are the ones that are primarily responsible for the flow of current. So, we can consider the movement of negative charges as the actual direction of the current.
Now, let's consider a battery with its positive terminal labeled as "+" and its negative terminal labeled as "-". When the actual direction of the current is from the negative to the positive terminal (opposite to the direction of the labeled "+" to "-"), the battery is being traversed against its own internal electric field. In this case, the change in electric potential or the battery's terminal voltage is negative.
On the other hand, when the actual direction of the current is from the positive to the negative terminal (the same direction as the labeled "+" to "-"), the battery is being traversed along its own internal electric field. In this case, the change in electric potential or the battery's terminal voltage is positive.
Therefore, based on our sign conventions, if a battery is traversed in the actual direction of the current in it, the sign of the change in electric potential or the battery's terminal voltage can be determined. If the actual direction of the current is from the negative to the positive terminal, the change in electric potential is negative. If the actual direction of the current is from the positive to the negative terminal, the change in electric potential is positive.