According to Joule's law, if the potential difference across a conductor having a material of specific resistance remains constant, then the heat produced in the conductor is directly proportional to [MP PMT 1986]

• A.            \[\rho \]                                 
• B.            \[{{\rho }^{2}}\]
• C.            \[\frac{1}{\sqrt{\rho }}\] 
• D.            \[\frac{1}{\rho }\]