Electric Field Strength: 2009 HSC Exam Question Explained | Australia

AI Thread Summary
The discussion revolves around calculating electric field strength using the formula E = V/d, with specific reference to a 2009 HSC exam question. The initial calculation of electric field strength as E = 100/0.10 resulted in 1000 V/m. A question arose about how the electric field strength would change if the positively charged plate was at +100V, leading to a corrected value of 2000 V/m. Clarification was provided that the voltage difference across the plates is not doubled, as the positive terminal is only +10V relative to the negative terminal at 0V. The conversation highlights the importance of understanding voltage differences in electric fields.
123ryoma12
Messages
8
Reaction score
1
upload_2015-9-20_16-36-16.png

This is from the 2009 HSC exam. (I'm in Australia)
I checked the answers and found that electric field strength was
E = 100/0.10 = 1000
My question is, what would the electric field strength be if the positively charged plate was +100V instead of 0V
Would it be 200/0.1 = 2000?
Is the formula E = The difference in volts between the two plates / distance.
Please help this has been bugging me.
 
Physics news on Phys.org
123ryoma12 said:
E = 100/0.10 = 1000
No it was not. The electric field strength is a dimensionful quantity and you simply cannot quote it as just a number without a unit. The field strength is 1000 V/m = 1 kV/m.

123ryoma12 said:
Would it be 200/0.1 = 2000?
It would be 2000 V/m.
 
I just realized that I shouldn't have posted here. Sorry about that.
But another question
http://www.regentsprep.org/Regents/physics/phys03/aparplate/plate3.gif
In this gif where
E = V/d
Shouldn't it be E = 2V/d
as there is voltage going to the positive and negatively charged plate for example
if the battery has 10V
The negatively charged would be -10V and the positively charge would be 10V
 
123ryoma12 said:
Shouldn't it be E = 2V/d
as there is voltage going to the positive and negatively charged plate for example
if the battery has 10V
The negatively charged would be -10V and the positively charge would be 10V

why would you think that ?
There isn't a 20V difference across the plates
one terminal of the battery, the positive, is +10V relative to the 0V of the negative terminalDave
 
Oh ok thanks. I just thought that for some reason. I didn't really know how the battery worked.
 
  • Like
Likes davenn
Thread 'Motional EMF in Faraday disc, co-rotating magnet axial mean flux'
So here is the motional EMF formula. Now I understand the standard Faraday paradox that an axis symmetric field source (like a speaker motor ring magnet) has a magnetic field that is frame invariant under rotation around axis of symmetry. The field is static whether you rotate the magnet or not. So far so good. What puzzles me is this , there is a term average magnetic flux or "azimuthal mean" , this term describes the average magnetic field through the area swept by the rotating Faraday...
Back
Top