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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.
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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 Vab=e-Ir See Example 19-7 Analyzing a circuit.
19-3 Kirchhoff’s Rules • Kirchhoff’s 1st 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 2nd 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… DV=IR… and the sign is negative to show the drop…see p 565 Figure 19-12.
19-4 Solving Problems with Kirchhoff’s Rules • Designate the current flow in each part of the circuit with a subscript. I1, I2, …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 • P582 18-21,24-28 due Monday BOP