(E&M) Don't understand why terminals of battery are switched

In summary, in the Princeton Review Cracking the AP Physics C Exam 2011 Edition book, example 11.9's solution involves a circuit where one of the batteries' terminals are swapped. The author's mention this and explain that the potential drops as a result of going from positive to negative, even though originally it was negative to positive. The solution involves using Kirchhoff's Rules to determine the current through R2. The reader is also confused about why the author's would switch the terminals, but it is later clarified that it was probably just a 'typo' in the original circuit diagram.
  • #1
nazopo
2
0
In the Princeton Review Cracking the AP Physics C Exam 2011 Edition book on example 11.9's solution, one of the batteries' terminals are swapped (the battery with 10V). I am not sure why the author's do this considering the current is drawn the same. Later on in the solution, they recognize that the terminals are switched when they state that the potential drops as a result of going from positive to negative (even though originally it was negative to positive).

PROBLEM:
Use Kirchhoff's Rules to determine the current through R2 in the following circuit:
l2eZ37Vl.jpg


WHERE I'M LOST:
I circled the parts of the illustration where the battery terminals are switched.
0a5xpaBl.jpg


During the explanation of the solution, it states that "From e to f, we travel through E2 from the positive to the negative terminal, so the potential drops by E2." so their intentions were to switch the terminals but I'm not sure why we are allowed to do that.

Here is a full page scan of most of the solution(the little bit that is not included here is not necessarily essential in this case)
Dv8JrZjl.jpg
 
Last edited:
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  • #2
You're not allowed to do that. The original circuit diagram probably just has a 'typo.'
 
  • #3
Ok, I see now. Thanks for the clarification.
 

1. What is the purpose of the terminals on a battery?

The terminals on a battery are the points where electricity enters and exits the battery. They are the connection points for a circuit to be completed, allowing the flow of electrons from the negative terminal to the positive terminal.

2. Why do the terminals on a battery need to be switched?

The terminals on a battery need to be switched in order to change the direction of the flow of electrons. This is important for different types of circuits, as well as for charging and discharging the battery.

3. How do I know which terminal is positive and which is negative?

The positive terminal on a battery is usually marked with a plus sign (+) and the negative terminal is marked with a minus sign (-). Additionally, the positive terminal is usually slightly larger in size than the negative terminal.

4. What happens if I switch the terminals on a battery?

If you switch the terminals on a battery, it will reverse the direction of the flow of electrons. This can cause damage to electronic devices or disrupt the functioning of a circuit.

5. Is it possible for a battery to have more than two terminals?

Yes, it is possible for a battery to have more than two terminals. Some batteries, such as car batteries, have multiple terminals for different connections. However, the basic function of the terminals remains the same - to complete a circuit and allow the flow of electrons.

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