how a resistor works
As you can imagine, resistance will depend on a material a resistor is made of.
For any given substance, resistance depends upon length and diameter of the conducting pathway. Resistance varies directly with length and inversely with cross-sectional area of the pathway.
In other words, you can express a resistance as:
R=ρ*L/A, where ρ represents resistivity of a material, L=length, and A=cross-sectional area.
(The values of ρ for materials such as silver-the best known conductor-, copper, gold, .. etc, you can find in easily somewhere on the net).
Is it enough, or would you like to go into atom(s)-electron(s) structure of a resistive material?
regards ..
InaP