Question

define Ohm's law and limitations

Answer 1

the act of controlling the size or extent of something is known as limitation

Ohm's Law deals with the relationship between voltage and current in an ideal conductor.

Answer 2

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality. I = V/ R

If you read Ohm's law as resistance is proportional to voltage, then: 

temperature is the one limitation, resistance varies with temperature, and depending on materials, it can vary a lot. 

Another is breakdown voltage, any device will start conducting more current than normal if the voltage is high enough, either through internal voltage breakdown or external arcing through the air. 

Semiconductor junctions are an obvious limitation also.