I would really appreciate some clarification about how to draw graphs showing changing flux and induced EMF. I understand that there needs to be a 90 degree phase difference as the EMF is a maximum when the flux has the greatest rate of change. However, our exam board says that the EMF can be either leading or lagging by 90 degrees. I don't understand this as surely the as the the EMF = negative gradient of flux then the EMF must be negative when the flux is a positive gradient and vice versa. Please help. This is driving me mad!