Question

The electric power consumed by a
device may be calculated by using either of the two expressions P =

I2R or P = V2/R . The first expression indicates that it
is directly proportional to R where as the second

expression indicates inverse
proportionality. How can the seemingly different dependence of P on R in these

expressions be explained?

Answer 1

Current is directly proportional to voltage by ohms law.
power is nothing but VI
substitute V=IR if the voltage is constant....you get I2R
substitute I=V/R if the current is constant ...you get V2/R
this is similar to the derivation of the equation of joules law 

Answer 2

Current is directly proportional to voltage by ohms law.

power is nothing but VI

substitute V=IR if the voltage is constant....you get I2R

substitute I=V/R if the current is constant ...you get V2/R

this is similar to the derivation of the equation of joules law.