Why Does Moving a Negative Charge to a Higher Potential Increase Its Energy?

[Kelly McGuire]

Homework Statement

When a -2C is moved from point A to B, the potential energy of the system increases by 10J. What is the voltage V(ab)?

Homework Equations

U=qV

The Attempt at a Solution

10=(-2)V, I thought the voltage was -5V but the correct answer is +5V. Could someone explain why this is?

 

[cnh1995]

What is the voltage V(ab)?

Vab is nothing but Va-Vb. In simple words, if you have a positive charge and a negative charge placed close to each other, you'll observe a gain in potential energy of the negative charge if it is moved away from the positive charge. Here, since the negative charge is gaining energy, point A must be at a higher potential (more +ve than B) than point B. Hence, Vab= +5V.