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

[belledona]

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!

 

[Dale]

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.

 

[belledona]

positive

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?

 

[Dale]

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?