1. EMF and Terminal Voltage

2. A device such as a battery or an electric generator that transforms one type of energy (chemical, light and so on) into electric energy is called a source of electromotive force, or emf.

4. Kirchhof’s Rules

5. Junction Rule
At any junction point, the sum of all currents entering the junction must equal the sum of all currents leaving the junction.

6. Loop Rule
The sum of the changes in potential around any closed path of a circuit must be zero.

7. Solving Problems with Kirchhof’s Rules

8. Important: the number of equations must be the same as number of unknowns!!!

9. In applying the loop rule, follow each loop in one direction only
In applying the loop rule, follow each loop in one direction only! (clockwise or counterclockwise – your choice).

10. Take the signs: For A Resistor:
IR if your chosen loop direction is the same as the chosen current direction.
+ IR if the directions of loop and current chosen are opposite.
For A Battery:
+e if your loop direction moves from the negative terminal to positive.
-e if your loop direction moves from the positive terminal to negative.