1. Electricity

2. What is electricity?
The flow of charge
Mostly, we focus on the flow of electrons in “normal” matter
With static electricity, we get a good “zap”
But we cannot stand around all day with Fluffy trying to keep the lights on

3. Sources of electric charges
Chemical
Batteries
Mechanical
Generators
Hydro, thermal, nuclear (thermal)
Solar
Solar cells
In every case, the source provides electrons with a “push” that makes it run around in a path (“circuit”)

4. What is “voltage”?
Batteries
1.5V 6V
12V
AC electricity
120V
240V
7500V
115000V
Voltage is the “push” electrons have in a circuit

5. What is a circuit?
A circuit has three elements
A conductor
A potential difference or “voltage”
A closed loop

6. An electric circuit is composed of what 3 elements?
Conductor, potential difference, closed loop
The “push” is called voltage, and is measured in Volts.
The flow of electrons is called current, and is measured in Amperes or Amps.
The flow of electrons is hindered by resistance, measured in Ohms.

7. Ohm’s Law Mnemonic

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

10. Examples How does this work?

11. Electrical Power
P= IV “Poison Ivy”

12. Electrical Energy
Hand Generator

13. 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

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

15. Low resistance
Short
Fat
cold

16. High Resistance
Long
Thin
Hot

17. Diagramming circuits

18. Series Diagram

19. 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