How does a resistor "resist" current/potential?
I know it's an elementary question, but I'm sure others are wondering too.
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Just as it happens I'm reading this application note by Vishay titled "Basics of Linear Fixed Resistors", which explains the construction of PTH and SMT fixed resistors.
Most resistors have a resistive layer on the surface of a non-conductive carrier, either carbon or metal-based or thick film. The resistance value is obtained by laser-cutting lines in the film.
The simplest is just a wirewound resistor. Metals are not perfect conductors, so a long thin piece of wire will have a predictable resistance to it. Cram it inside a little component by wrapping it into a helix.
There are many other types, too, using thin films, etc:
As for what causes resistance, a simple explanation is that it's analogous to friction. It converts electrical energy into heat energy, the same way friction converts mechanical energy into heat energy.
For a more detailed description, you need to get into physics. In metals, like a wire-wound resistor, "the thermal motion of ions is the primary source of scattering of electrons (due to destructive interference of free electron waves on non-correlating potentials of ions), and is thus the prime cause of metal resistance"
Here is a link which I suppose, will definitely quench your thirst if nothing else has yet.
Inside a carbon resistor is a 'ceramic 'core' on which is deposited a spiral carbon 'track'. The track may have been machined, or 'burnt' away with a laser beam.