Describe ohm's law and its limitations;

The Ohm's Law is a powerful and simple tool to analyze electric circuits. It shows the relationship between voltage (V) and current (I) in a conductor. But, in order to properly apply to circuits (real circuits), its limitations must be understood.   Most conductors, resistance is greatly unaffected by current or voltage (resistance is stable property).
Limitation: this law does not apply to rectifiers or semiconductors or to the conduction of electricity through gases.
Formula: current (I) is equal to voltage (V) over resistance (R)