2. An electric circuit is composed of 3 elements Conductor, potential difference, closed loop An electrical circuit without a load that has some resistance is essentially a short circuit (Think about the batteries in the simulation) (An ammeter has very little resistance. Think about my poor ammeters in a circuit with no loads or other resistance.) Electrical Circuits

3. In a series electric circuit all of the electrons must flow through the same elements In a parallel electric circuit electrons may flow through different circuit elements Electrical Circuits

4. In a series electric circuit, the voltage drops as it flows through each resistive circuit element Electrical Circuits

5. Resistors in Series: Building Analogy To go from the top to the bottom floor, all people must take the same path. So, by definition, the staircases are in series. With each flight people lose some of the potential energy given to them by the elevator, expending all of it by the time they reach the ground floor. So the sum of the V drops across the resistors the voltage of the battery. People lose more potential energy going down longer flights of stairs, so long stairways correspond to high resistance resistors. The double waterfall is like a pair of resistors in series because there is only one route for the water to take. The longer the fall, the greater the resistance. 3 steps 6 steps 11 steps Elevator (battery) R 1 = Lamp R 2 = Lamp R 3 = Lamp R1R1 R2R2

6. Diagramming circuits

7. Series Diagram

8. Ohm’s Law: Ohm's Law …says that, for many materials under a wide range of conditions, the voltage, V, and current, I, are linearly related, which implies resistance, R, is independent of V and I. When does it not apply? (Most important case)

9. Ohm’s Law Mnemonic

10. Questions When a battery is connected to a complete circuit, charges flow in the circuit almost simultaneously. Why?

11. Resistance and Ohm’s Law Resistance is the impedance to the flow of charge Resistance is defined as the ratio of potential difference to current R = V/I Unit is the Ohm, Ω A device is said to obey Ohm’s Law of its resistance is independent of the Voltage

12. Find Resistance of a material Depends on four factors –R ∞ Temp –R ∞ RHO (ρ) resitivity –R ∞ Length –R ∞ A -1 (cross-sectional Area)

13. Low resistance Short Fat cold

14. High Resistance Long Thin Hot

15. Parallel Circuit More than one path for the flow of charge More room for the flow of charge so Resistance goes down Voltage must stay the same since all charges have the same drop