19-2 EMF and Terminal Voltage A battery or generator, or other electrical energy creation device, is called the seat or source of electromotive force, emf. Batteries have internal resistance. Terminal voltage V ab =e -Ir See Example 19-7 Analyzing a circuit.

19-3 Kirchhoff’s Rules Kirchhoff’s 1 st or junction rule is that at any junction point, the sum of all currents entering the junction must equal the currents leaving the junction. Kirchhoff’s 2 nd rule or loop rule is that the sum of the changes in potential around any closed path of a circuit must be zero.

19-3 Kirchhoff’s Rules Between the two ends of a resistor, the voltage drops… D V=IR… and the sign is negative to show the drop…see p 565 Figure

19-4 Solving Problems with Kirchhoff’s Rules Designate the current flow in each part of the circuit with a subscript. I 1, I 2, …etc. See Example 19-8 Using Kirchhoff’s rules. See p 566 and p567

19-5 EMFs in Series and Parallel When 2 or more EMFs are placed in series, the algebraic sum of their potentials is the total potential for the circuit. Remember their internal resistance is a factor. Series with + to+ and – to – are used for charging and the sum is up then down… See p 568 a,b,c

19-5 EMFs in Series and Parallel EMFs placed in parallel maintian the same voltage, but provide more current.

HOMEWORK P ,24-28 due Monday BOP