I am confused how a charge could have negative work done.(adsbygoogle = window.adsbygoogle || []).push({});

To clarify, I was doing a problem earlier in which a positive charge and negative charge are moving towards each other. I used the equation

work = Δv * q

And when I was doing this, the change in electric potential, Δv, was negative, and the charge i was moving, q, was positive. That means the work was negative.Let's say that it was -5 Joules.

I realize that this work, -5 Joules, is thechange in electric potential energy. I assume it is negative because when the two unlike charges move together, no work is required because the two are moving together naturally, which means the electric potential energy is transferring to kinetic energy, thus making anegativechange in electric potential energy because it is decreasing.

However, lets say I wanted to use this work value, -5 Joules, in the formula w = f * d to find the force for the distance d that the charge traveled. Do I choose to use -5 Joules or positive 5 Joules? I am conflicted because:

1. The charge is moving in the direction of the attractive force between it and the negative charge, thus making me want to choose the positive 5 Joules

2. No work was required to even move the positive charge to the negative charge, so it could be wrong to use w = f*d

3. The charge had a w value of -5 Joules, so if I just used that directly for the w = f * d equation, my force would be negative which does not make any sense at all.

I guess what I'm really asking is:

Is work done when a positive charge and a negative charge move together, and if so, is that work positive or negative?

I realize that my question might be extremely confusing, if you want me to explain something that I said I will be more than happy to.

Thank you

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# B Negative work and electric potential energy

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