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Where Does Current Come From?

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. Circuit Components. Batteries. +. +.

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Where Does Current Come From?

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  1. 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. EGR 101

  2. Circuit Components • Batteries + + EGR 101

  3. 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 EGR 101

  4. 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). EGR 101

  5. Current Direction We will adopt “Conventional Flow” for all of our work! EGR 101

  6. 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 EGR 101

  7. 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. EGR 101

  8. When batteries are connected with their polarities in the same direction, they are in a series-aiding arrangement. EGR 101

  9. When batteries are connected with their polarities in the opposite direction, they are in a series-opposing arrangement. EGR 101

  10. In Class Activity • What is the total voltage between terminals A and B in the figure below?Which terminal is at a higher potential? A B 9V 4V 15V EGR 101

  11. Introduction to Ohm’s Law • A 1 Ohm resistance limits the current to 1 Amp when 1 Volt is applied. V = I.R EGR 101

  12. Ohm’s Law • Three forms: • Use the form that best describes the quantity that you are trying to determine EGR 101

  13. Determine the Current I + _ EGR 101

  14. Determine the Voltage + _ EGR 101

  15. Determine the Resistance + _ EGR 101

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