Two heating coils A and B made of the same material are connected in parallel across yhe mains.The length and diameter of A are twice those of B.In which will more heat be produced and by how much?

R_B =(ρl)/(∏(x/2)²)                                              let x be the diameter of the coil B

R_B = (4ρl)/(∏x²)

R_A = (ρ2l)/(∏x²)

on comparing the resistance of these two we will get 

2R_A = R_B

applying the formula P= V²/R

since the value of R_A is smaller than R_B then the heat energy will be more in the A coil.