Does U=qV or -qV? I notice my textbook uses qV but

In summary, U=qV is the correct formula for electric potential. The force is different and points in the direction of decreasing potential for a positive charge. The change in U=qV would be negative if the charge moves in the direction of F=qE. However, it is important to note that the negative sign is only used in specific cases and can be confusing, so it is important to pay attention to the context of the problem.
  • #1
belledona
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Hi I have a question about electric potential! Since the negative sign isn't used in U=qV, and a-b is used for subscripts, then that takes care of the negative. But what about using U=-qV? An online lecturer uses U=-qV, while my textbook uses U=qV and then uses -qV to explain the force used to move a charge AGAINST the electric field. I'm wondering if qV or -qV is convention, because -qV is easier for me to understand conceptually but I lose the negative sign sometimes during problems...

Thank you!
 
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  • #2
U=qV is correct.

The force is different, so don’t get confused about that. The force on a positive charge points in the direction of decreasing potential.
 
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  • #3
Dale said:
positive

Dale said:
U=qV is correct.

The force is different, so don’t get confused about that. The force on a positive charge points in the direction of decreasing potential.
hi, thanks for your answer! so U=qV would only be negative if F=qE --> q=F/E (force is negative) here?
 
  • #4
Essentially yes, but the way you wrote it is a bit sloppy. To make it correct you would need to say:

The change in U=qV would be negative if q moves in the direction of F=qE here?
 

Related to Does U=qV or -qV? I notice my textbook uses qV but

1. What is the difference between U=qV and -qV?

The only difference between U=qV and -qV is the sign in front of the term qV. This sign indicates the direction of the electric potential energy. In U=qV, the positive sign indicates that the potential energy is positive and the electric force is repulsive. In -qV, the negative sign indicates that the potential energy is negative and the electric force is attractive.

2. Why does my textbook use qV instead of -qV?

Some textbooks may use qV instead of -qV to simplify the notation and make it easier to understand. However, it is important to understand the significance of the sign in front of the term qV and how it affects the direction of the electric potential energy.

3. Can I use either U=qV or -qV in my calculations?

Yes, you can use either U=qV or -qV in your calculations as long as you understand the significance of the sign and use it correctly. The final result should be consistent with the direction of the electric potential energy.

4. How does the sign in front of qV affect the electric potential energy?

The sign in front of qV determines the direction of the electric potential energy. As mentioned before, a positive sign indicates that the potential energy is positive and the electric force is repulsive, while a negative sign indicates that the potential energy is negative and the electric force is attractive.

5. Is there a preferred notation for electric potential energy, U=qV or -qV?

There is no preferred notation for electric potential energy. Both U=qV and -qV are commonly used in different textbooks and literature. It is important to understand the significance of the sign and use it correctly in your calculations.

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