Electric Field Question. Really need help!!!?

Question

I am stuck on this problem and wondering if someone could offer some assistance. How does one find the individual values for Vb, Va, etc. without any given point charges. I've been using the equation delta(V)=-Ed and using that equation I was able to get A correct. It's not working for B and C though. I'm not sure how to determine the different potentials when I have no values for the point charges. Can anyone offer some assistance? I've been working on this problem for the better part of the last two days and I'm quite frustrated

The drawing shows a uniform electric field that points in the negative y direction; the magnitude of the field is 1600 N/C.

http://www.webassign.net/CJ/p19-32.jpg

a) Determine the electric potential difference VB - VA between the points A and B.
The answer here is 0 V.

(b) Determine the electric potential difference VC - VB between the points B and C.
V

(c) Determine the electric potential difference VA - VC between the points C and A.
V

Answer 1

I understand your frustration. This is one of the most challanging topics in introductory physics. First of all we have to figure out what electric field and potential tell us about the problem.

What is electric field? Let's think for a second, we have a constant electric field, what does that mean? Electric field essentially tells us how a charged particle will interact in this region. Positive charges will move with the field while negative charges will move opposite the field. Also, stronger charges will experience greater forces as a result of the field. I will only use positive charges to compare this to maybe a more familiar situation, gravitational field. Massive objects move in the same direction as the gravitational field and the force they experience as a result of that field (called weight) is proportional to thier mass. The same is true with positively charged particles in an electric field. They will move in the direction of the field and experience a force proportional to thier charge.

Electric Potential is a measure of potential energy a charged particle has. Positive charges will tend to move from higher potentials to lower potentials, negative charges act in the opposite way. We can assume that any point can be defined as "zero" potential. Sounds alot like gravitational potential energy to me. You increase electric potential when you move the opposite direction that a positive charge would want to move in the field. You must do work to push a positive charge to a higher potential. This is similar to lifting a massive object to increase its potential energy.

You state the correct relationship between E and V as the charge of the particle is not relevant the way E and V are defined.

dV = - E d

Remember that d is the distance you travel with or against the electric field IN THE DIRECTION OF THE ELECTRIC FIELD. From B to A or A to B, we travel a distance, but we travel exactly perpendicular to the field thus there is no potential difference between A and B in either direction.

If we look at C to B, we see that we travel 8.0 cm with the E-field in exactly the same direction as the E-field. The value d is equal to 8.0 cm in the equation so we get. Note: The unit 1 N/C is the same as 1 V/m.

dV = -1600 V/m * (0.080m) = -128 V

Now we will go from C to A and we travel a distance of 10.0 cm at an angle to the electic field. We know from the picture that we can actually say we traveled 6.0 cm to the -x and 8.0 cm to the -y by breaking our vector up into components. The potential difference is then the sum of potential differences of these to sections. We can see that 6.0 cm to the -x direction is the same as traveling from B to A or 0 V and 8.0 cm in the -y direction is the same as traveling from C to B or -128 V, so if we add these two together we get the potential difference from C to A which is -128V.

Answer 2

Electric subject E= - dV /dr As talents is consistent dV / dr =0 Hence electrical subject is 0 in a vicinity wherein electrical talents is consistent. For instance, within a hole charged matallic sphere, THE ELECTRIC FIELD IS ZERO BUT THE POTENTIAL INSIDE IS CONSTANT and identical to talents at the suface of charged sphere

Answer 3

I would point a magnet at the whole mess