PHYS345 Electricity and Electronics

Series Circuits
Three resistors in series
  Equivalent simple circuit
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.

i = i1 = i2 = i3

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.

V = V1 + V2 + V3

Combining the two equations via Ohm's law:

V = i1R1 + i2R2 + i3R3
  The simple equivalent circuit is required to have the same current through the battery, given the same applied voltage:
V = i (R1 + R2 + R3)
V = i Req

Comparison of the equations above yields:

Req = R1 + R2 + R3

Resistors in series

Last updated Sept. 2, 1998.
Copyright George Watson, Univ. of Delaware, 1998.