1. Electrical Potential Joules units: = Volt = V Coulomb
The amount of work that can be done by some charge moving in a circuit. W
V = q
Joules
units:
= Volt = V
Coulomb

2. Current
The movement of electrons through a conductor. The rate at which charge flows. q
I = t
Coulombs
units:
= Ampere = Amp = A
Second
DC (Direct Current) – All charges move in one direction in the circuit.
AC (Alternating Current) – charges move one way and then the other, changing direction from moment to moment.

3. A path where electrons flow and their energy is used.
CIRCUIT:
A path where electrons flow and their energy is used.
RESISTANCE:
Opposition to the flow of electrons in a circuit.

4. THE DAM ANALOGY Dam = Battery, Outlet, Power Supply
Water Wheel = Energy User/Converter (Light Bulb, Motor…)
Water Depth =
V = Voltage or Potential
Pipe = Wire
Current
Valve = Resistance or Current Control
GROUND or Lowest Potential

5. How can the resistance change?
What are the variables that effect the resistance of the flow of the water in the Dam Analogy?
Resistance is much like friction. The more “friction” against a current, the more resistance.

6. First variable What would happen if we widen the path for the water?
The resistance would be less.
Therefore: R is in proportion to 1/A

7. 2nd variable What would happen if we shorten the path of the valve?
There would be less to flow through, therefore the resistance would be less.
Therefore, R is proportional to L

8. 3rd variable
What would happen if we thicken the walls of the pathway for the water?
There would be more resistance.
Therefore, R is proportional to density of the material.

9. 4th variable What would happen if we heat up the pathway of the water?
The resistance would increase
As resistance goes up, temperature goes up.

10. Summary Resistance of an object depends on
Cross-sectional area of the resistor
Length of the resistor
Density of the resistor
Temperature of the resistor

11. DECREASES! As R increases, I ……
What does the dam analogy tell us about the relationship between I and R?
As R increases, I ……
DECREASES! or

12. Increase the “push” or VOLTAGE
How could the current be increased in a circuit whose resistance is held constant?
Increase the “push” or VOLTAGE

13. Georg Simon Ohm Ohm’s Law: UNITS FOR RESISTANCE Can Be Written As:
More Typically Written As:
This tells you the number of volts necessary to push 1 amp of current through the device.

14. Power Deriving power of a circuit P = Work/time
How is work related to potential of a circuit?

15. PRACTICE PROBLEMS I = 0.033A t = 50 s
1. If it took 5 minutes for 10 C to flow in a circuit, what was the current while the circuit was working?
2. How long would it take for a 10 A stove top to pass 500 C of charge?
I = 0.033A
t = 50 s

16. PRACTICE PROBLEMS V = 47.5 V R = 600Ω
3. What is the voltage on a circuit that has a resistance of 95Ω and a current flowing through it of 0.5 A?
4. What is the resistance of a circuit that is hooked up to a 12 V battery and has 0.02 A flowing through it?
V = 47.5 V
R = 600Ω