Problem $7\mathrm{.}58$ A transformer $($Prob$.7\mathrm{.}57)$ takes an input AC voltage of amplitude V$1,$ and delivers an output voltage of amplitude V$2,$ which is determined by the turns ratio $($V$2/$V$1=$ N$2/$N$1).$ If N$2>$ N$1,$ the output voltage is greater than the input voltage. Why doesn$$t this violate conservation of energy? Answer: Power is the product of voltage and current; if the voltage goes up$,$ the current must come down. The purpose of this problem is to see exactly how this works out, in a simplified model.