# Homework Help: Voltage Change and KE

1. Sep 19, 2006

### NotMrX

If a electron slows down while moving due to an electric field we would say the potential decreases. If a proton slows down while moving into an electric field does potential increase? I am confused because:

$$\Delta KE=q\Delta V=\frac{m(v^2_f-v^2_i)}{2}$$

but I would get opposite signs for the voltage in those cases that I thought I was supposed to.

2. Sep 19, 2006

### zigga15

This formula is more quantifying the KE, so i wouldnt use it to figure out your answer. Consider what potential is, its the potential to do something. If an electron is traveling at a high velocity you need to put more energy into it to make it go faster (if that energy is a magnetic field or whatever). If the electron was going slower it would take less effort to make it go faster so Id say when the electron slows down the electrons potential increases. Someone correct me if im wrong because i probably am, lol... Hope this helps

3. Sep 19, 2006

### NotMrX

Now I am thinking that maybe we just use the magnitude of the charge. If the electric field is constant, then if the particle speeds up its potential decreases since the energy went into speeding it up. If the particle slows down then it seems like the potential energy increases so then the electric potential increases. However in the book i was reading it said the potential for an electron that's speed slowed down in a constant electric field decreased and ussually it is me that is wrong and not the book