Some

 har vakt kuch karte raho bas or kuch nhi q ki khali tu sab kuch he lekin os khali me bhi bohut kuch sikhna he

(1)Non-ohmic condutor do not obey ohm's law (2)in non-ohmic resistors there is no linear relationship  (3) Potential difference  (V)versus current  (I)current is not a straight line (4)Expression for resistance R=lim delta V/delta I E.g liquid electrolytes ,vacuum tubes,