Question

Two resistence wires of the same material and of equal lengths and equal diameters are first connected in parallel and then in series in an electric circuit. What is the ratio of heat produced in parallel and series combination?

Answer 1

R1 = R2 = R

voltage across them = V = battery potential
Series :  net resistance = 2R
              current =  V/(2R)  
           heat =  power = I^2 R + I^2 R = V^2/(2R)

parallel:   
         heat =  power = V^2/R + V^2/R =  2 V^2/R

Ratio  : parallel / series = 4