AP Physics B : Using Faraday's Law
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Example Questions
Example Question #1 : Electromagnetism
An ideal transformer, under a purely resistive load, consists of an iron core that directs all the magnetic flux from a primary winding through a secondary winding. The primary winding has 
In basic consideration, the electrical transformer works directly according to Faraday’s law, following the picture given below.
If the coils are wound tightly enough that the magnetic flux generated in any of them effectively passes undiminished through all of them, and the iron core directs all the magnetic flux from the primary to secondary coil with insignificant losses, then Faraday’s law points a direct path from 
If there are 
From the figure, it is seen that the voltages in each line are dropped over all loops together. Hence, for the primary winding, by Faraday’s law:
For the secondary winding:
Here, 
This can be used to solve the problem above:
NOTE: This only works under alternating current. Otherwise, there is no change in current to create the changing magnetic flux on which the transformer depends.
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