Series Circuits 




Current is the same through each resistor; in essence that is the definition of "series,"
that one end of each resistor is hooked together and nothing else at that point.
The voltage difference supplied by the battery is shared by the three resistors. How the voltage is shared is determined by the relative resistance of each resistor.


Combining the two equations via Ohm's law:

The simple equivalent circuit is required to have the same current through the battery, given the same applied voltage:  



Comparison of the equations above yields:
