question_answer

Ohm's law is not obeyed by:

A) electrolytes       

B) discharge tubes

C) vacuum tubes                  

D) all of these

Correct Answer: D

Solution :

Key Idea: Ohm's law is true for metallic conductors only. According to this law, if there is no change in the physical state of a conductor (such as                                                temperature) then the ratio of the potential difference applied at its ends and the current flowing through it is a constant. If a graph be drawn between the applied potential difference V and the current \[i\] flowing through the conductor then it will be a straight line. Ohm's law is true for metallic conductors only. Hence, electrolytes, discharge   tubes and vacuum tubes do not obey Ohm's law.