• Voltage produced that could drive a current through a circuit ​

• εmf = electromotive force

• ​Not really a "force"

Electromotive Force

Internal Resistance

• Batteries and generators have resistance

  • In batteries resistance is due to chemicals

  • In generators resistance is due to wires and other components​

• Internal resistance is connected in series with the equivalent resistance of the circuit​

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Terminal Voltage

Multiple εmf sources

• If batteries are connected in series, their εmf's add, but so do their internal resistances.

• If batteries are connected in parallel their εmf​'s stay the same, but their currents add and the combined internal resistance is less.

• Think of this as resisters in series, parallel, or both; depending on the situation. ​