1. The problem statement, all variables and given/known data A 100 W transformer (Ns = 1500) has an input voltage of 9.0V and an output current of 0.65 A 2. Relevant equations P = IV Np/Ns = Is/Ip = Vp/Vs 3. The attempt at a solution The problem is that I'm not sure what a 100 watt transformer means. Assuming it means that it outputs, not inputs, 100 watts of power, then: P = IV 100 = 0.65 V V = 154 V Np/Ns = Vp/Vs Np/1500 = 9/154 Np = 87.66 turns. I feel that mathematically I am doing everything correctly, but I thought that because voltage was being increased then the amount of coils in the primary coil should be more than in the secondary. Thanks.