electricity - Why does a Resistor cause a potential drop?

I need to know the underlying physics of what exactly happens different with the electric field in the resistor than in superconducting wires.

Why is it that when I connect a resistor, potential drops across its(resistor's) ends? Sorry for the silly question but I can't figure it out. I do know, energy will be dissipated and hence the voltage will drop but I'm looking for a more insightful and detailed answer.

Answer

Electric potential is a potential energy just like gravitational potential energy or indeed any other form of potential energy. Specifically, moving one coulomb of charge through an electrical potential of one volt produces (or requires) 1 joule of energy. From your question I guess you're basically happy with this, so the question is really how this energy is dissipated i.e. what happens to that 1 joule of energy?

When you apply a voltage to the conductor you produce a force on the conduction electrons so they accelerate - the potential energy is turned into kinetic energy of the electrons. However conductors are made up from a crystal lattice of atoms/molecules that is randomly vibrating due to thermal energy, and there is a probability that the moving electrons will scatter off this lattice and transfer energy to it. So the electron is slowed down and the magnitude of the lattice vibrations is increased. Increased lattice vibrations mean the conductor is hotter, so the kinetic energy of the electrons has been transferred into thermal energy in the conductor.

And that's what happens to the 1 joule of energy. It's transferred to the conductor and ends up as heat.

Some related issues you might want to look into further: when you cool a conductor you reduce the magnitude of the lattice vibrations and you make it less likely the electron will scatter off the lattice. That's why resistance (usually) decreases with decreasing temperature. The superconducting transition prevents electrons from scattering off the lattice, so they can't transfer energy to it and that's why superconductors have a resistance of zero.