Ohm's law describes the fundamental linear relationship between electric potential difference, electrical current, and resistance in an ohmic conductor. When an electric potential difference V is applied across a conductor, the induced macroscopic electric field drives mobile conduction electrons through the crystal lattice against repeated collisions with vibrating metallic cations. The resulting steady drift current I is directly proportional to the applied voltage and inversely proportional to the total electrical resistance R, with microscopic dissipated power manifesting as Joule heating.