# Electric field

1. Jan 27, 2010

### quietrain

hi, i have a question.

if electric field is 20V/m for a 10 V parallel plates potential difference of distance 50cm, in accordance with the formula E = change in V / d then does it mean that as long as i have a 10 V potential difference, regardless of the orientation of the plates, like if i change the 10 V difference to a small +ve cylinder and a large -ve cylinder encompassing it, does the E field still remains as 20V/m if the distance is kept at 50cm?

so in other words, does the electric field E remain the same as long as the Volt difference i use is kept at 10V and the distance is 50cm? that means 10V difference at a distance of 50cm always give me E field of 20V/m?

oh by the way, does it matter if i measure the distance from the (-ve)0 V plate or from the (+ve)10V plate if i want to use in the formula E = V/d?

thanks!

2. Jan 27, 2010

### Born2bwire

That equation is only valid for parallel plate capacitors. You could probably use it as an estimation for concentric cylindrical plate capacitors though one would want to investigate the conditions under which the equation would still be accurate.

As for the last question, how would it matter?

3. Jan 27, 2010

### quietrain

ah i see... thanks

so would it be ok to use the linear charge density for this cylindrical example or is that only used for long thin rods? or am i suppose to use surface charge density?