Sorry for this novice thread but I've just started learning electronic and I've some problems to understand some concepts and I hope you guys can help me to grasp them, hopefully.
1) In my lesson book it says that the density of charges = D = Q/S (S = area).
Well that makes sens.
Then it says :
Q/S = D = E . ε. I'm not sure I get this last part on so many levels.
First of all I don't see why the substance between two charges comes to play a role in the value of a voltage or an electric field. How I see it at the moment is if two charges are bigger then the voltage is bigger. I don't really get that "ε".
2) Capacitance:
My book says the capacitance = C = Q / U . I just don't get it. First of all voltage must relative between two charges. Here we have Q, but which Q is it ? Any of the two Q of the two metallic plates ? Also for me the word capacitance means : If I have a bottle, the capacitance of that bottle is the amount of water I can put in that bottle before the water starts to come out.
I don't see the link between my definition of capacitance and C = Q / U, I just don't see how this formula can give any info on the capacitance of a capacitor since the Q is supposed to change over time.
( 3) In coulomb's law :
F = k . q.q' / d² with k = 1/ 4πε. Well I understand that there must be a proportionality between the two charges' magnitude and the force and an inverse proportionality with the distance. I don't get what the "k" role is there and how it's calculated. )
I'm really grateful if anyone could try to answer my questions because I'm really confused. My third question is the less important of the three for me tho.
1) In my lesson book it says that the density of charges = D = Q/S (S = area).
Well that makes sens.
Then it says :
Q/S = D = E . ε. I'm not sure I get this last part on so many levels.
First of all I don't see why the substance between two charges comes to play a role in the value of a voltage or an electric field. How I see it at the moment is if two charges are bigger then the voltage is bigger. I don't really get that "ε".
2) Capacitance:
My book says the capacitance = C = Q / U . I just don't get it. First of all voltage must relative between two charges. Here we have Q, but which Q is it ? Any of the two Q of the two metallic plates ? Also for me the word capacitance means : If I have a bottle, the capacitance of that bottle is the amount of water I can put in that bottle before the water starts to come out.
I don't see the link between my definition of capacitance and C = Q / U, I just don't see how this formula can give any info on the capacitance of a capacitor since the Q is supposed to change over time.
( 3) In coulomb's law :
F = k . q.q' / d² with k = 1/ 4πε. Well I understand that there must be a proportionality between the two charges' magnitude and the force and an inverse proportionality with the distance. I don't get what the "k" role is there and how it's calculated. )
I'm really grateful if anyone could try to answer my questions because I'm really confused. My third question is the less important of the three for me tho.