[Solved] Estimate induced emf in the coil 1. The problem statement, all variables and given/known data Consider a single-loop coil whose magnetic flux is given by this image: Estimate the induced emf in the coil at times near t = 0.3s, t = 0.4s and t = 0.5s This is for algebra-based physics. 2. Relevant equations emf = -N*(change in flux)/change in time 3. The attempt at a solution At t = 0.3s emf = -1(4- -4)/(0.4 - 0.2) = -8/0.2 = -40V At t = 0.4s Rate of change = 0 At t = 0.5s emf = -1(-4 - 4)/(0.6 - 0.4) = 8/0.2 = 40V My first and third answers are wrong. What've I missed? The text book has -0.06kV, 0 and 0.06kV but those answers are also incorrect. Edit: Solved it. This is the graph of 4 Cos[(2 Pi/(0.4))*x] Differentiating this gives y = -20pi*Sin[5pi*x] Evaluating it at t = 0.3 s gives 63V. I do not know why differentiation is used for an algebra-based physics problem when my TA explicitly told me to not use calculus, but there it is.