Ohm's law
For an ohmic conductor at constant temperature, the current is directly proportional to the applied potential difference: I ∝ V, or I = V/R (equivalently, V = IR). This relationship defines resistance as R = V/I. Ohm's law holds for most conductors over a wide range of conditions but fails for some materials (non-ohmic devices) like light bulbs (resistance increases with temperature) and diodes.
Formula
V = IR
Real World
When Tesla engineers design battery management systems, they rely on Ohm's law to calculate the voltage drop across internal resistance at high discharge currents, which directly limits a Model 3's acceleration.
Exam Focus
State 'at constant temperature' when quoting Ohm's law — examiners award a mark for this condition and penalise its omission.
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