Ok, I have a primary and secondary coil. I set up a transformer between them. Each has 400 turns of coil(N). The primary coil produces a potential difference of 2.988 V. The secondary coil has a potential difference of 0.0551 V. For the efficiency, I used the equation (Np*Vs)/(Ns*Vp) * 100% Np-turns of primary coil(400) Vs- potential difference of secondary coil(0.0551) Ns- turns of secondary coil(400) Vp-potential difference of primary coil(2.988) When I plug them in, I get 1.84% efficiency. Am I messing the formula up, plugging in the wrong values. etc? 1.84% seems awfully low. Thanks.