1. EGR 1011 Where Does Current Come From? The free electrons in a conductor need to be replaced when they move through the conducting medium (the wire). These electrons are replaced by electrons from a source of energy such as a battery.

2. EGR 1012 Circuit Components Batteries + +

3. EGR 1013 Source of Voltage in a Battery A chemical reaction within the battery separates positive and negative ions (charged atoms) When the battery is connected to a circuit, the negative charges move toward the positive terminal and a current is produced The amount of current is constrained by the resistance of the circuit

4. EGR 1014 Example of A Battery The source of energy E in (Joules) releases charges Q in (Coulombs) Voltage (V) – the difference in potential that uses E = one Joule (J) of energy to move a charge Q = one coulomb (C).

5. EGR 1015 Current Direction We will adopt “Conventional Flow” for all of our work!

6. EGR 1016 Mathematical Relationship E: Energy required to move charges in Joules (J). Q: Charge value in Coulombs (C). V: Voltage or potential difference across the battery's posts in volts (V). Thus, V = E / Q. In units: 1 Volt = 1 Joule/Coulomb

7. EGR 1017 Team In-class Activity (15 minutes) A 10 V source uses 2 Joules of energy per second. Calculate the current being used by the source. Hint, turn the word problem into equations; write down what you know.

8. EGR 1018 When batteries are connected with their polarities in the same direction, they are in a series-aiding arrangement.

9. EGR 1019 When batteries are connected with their polarities in the opposite direction, they are in a series- opposing arrangement.

10. EGR 10110 In Class Activity What is the total voltage between terminals A and B in the figure below? Which terminal is at a higher potential? 9V4V15V AB

11. EGR 10111 Introduction to Ohm’s Law A 1 Ohm resistance limits the current to 1 Amp when 1 Volt is applied. V = I. R

12. EGR 10112 Ohm’s Law Three forms: Use the form that best describes the quantity that you are trying to determine

13. EGR 10113 Determine the Current + _ I

14. EGR 10114 Determine the Voltage + _

15. EGR 10115 Determine the Resistance + _