Question

Derive expression for effective power parllel combination

Answer 1

Current I is a constant in series combination

P1=I2R1

P2=I2R2

Adding the above two equations

P1+P2=I2(R1+R2)⟹Peff=I2Reff

Parallel

Voltage V across the resistors are taken to be a constant

P1=V2R1

P2=V2R2

Adding the above two equations

P1+P2=V2(1R1+1R2)⟹Peff=V2Reff

In both cases I get the same e9xpression for Peff. Obviously this is wrong. But I'm not sure where I'm going wrong. Help is appreciated.