# Homework Help: Electric Potential Problems Need Help

1. Oct 11, 2006

### chillaxin

Electric Potential Problems Need Help ASAP!!!

The anode (positive terminal) of an x-ray tube is at a potential of +125000V with respect to the cathode (negative terminal). a) how much work (in Joules) is done by the electric force when an electron is accelerated from the cathode to the anode? b) if the elctron is intially at rest, what kinetic energy does the electron have when it arrives at the anode?

Point A is at a potential of +250V, and point B is at a potential of -150V. An a-particle is a helium nucleus that contains two protons and two neutrons: the neutrons are electrically neutral. An a-particle starts from rest at A and accelerates toward B. When the a-particle arrives at B, what kinetic energy (in elctron volts) does it have?

An electron and a proton are intially very far apart (effectively an infinite distance apart). They are then brought together to form a hydrogen atom, in which the electron orbits the proton at an average distance of 5.29x10^-11m. What is the EPE(final)-EPE(initial+) which is the change in the electric potential energy?

A capacitor has a capacitance of 2.5x10^-8 F. In the charging process, electrons are removed from one plate and placed on teh other plate. When the potential difference between the plates is 450V, how many electrons have been transferred?

Two capacitors are identical, except that one is empty and the other is filled with a dielectric (k=4.50). The empty capcitor is connected to a 12.0V battery. What must be the potential difference across the plates of the capacitor filled with a dielectric such that it stores the same amount of electical energy as the empty capacitor?

2. Oct 11, 2006

### Staff: Mentor

-1- Hint -- Look up the energy conversion from electron volts (eV) to joules (J).

On the others, you need to show some work in order for us to help you.

3. Oct 11, 2006

### quasar987

And emphasizing the rules of the forum according to which you must show some work in order get help.

4. Oct 11, 2006

### Staff: Mentor

The PF has been up and down over the past few days. Probably it crashed about the time you posted?

5. Oct 11, 2006

### quasar987

I found out. It's just that our friend chillaxin has made the exact same post one the 'Advanced Physics' forum. :p