1. 7-2: Electric Current

2. 1. Voltage
Charges flow from areas of high voltage to areas of low voltage
A voltage difference must be present for electrical charges to flow
By definition, voltage difference is the push that causes charges to move
Measured in volts (V)

3. 2. Circuit A circuit is a closed, conducting path
For electric charges to flow, the wire must always be connected in a closed loop, circuit.

4. 3. Electric Current
An electric current is the flow of charges through a wire or any conductor
Typically, is the flow of electrons
Measured in amperes (A)

5. 4. Static Discharge vs Flowing Current
Static discharge – charges move from one place to another in a short period of time
In order to keep a current flowing, a device must be present that maintains a voltage difference

6. 5. Dry Cell Batteries Typical battery
Voltage difference between the positive and negative terminals
Moist chemical paste with a solid carbon rod in the middle

7. 5. Dry Cell Batteries

8. 6. Other Sources
Wet Cell Battery – two connected plates in a conducting solution
Car Battery – six connected plates
Wall sockets/electrical outlets

9. 7. Resistance
Resistance is the tendency for a material to oppose the flow of electrons….changing electrical energy into thermal energy and light
Measured in ohms ()
Copper – low resistance
Example – light bulb

10. 7. Resistance

11. 8. Factors That Affect Resistance
For more efficient energy flow….want a wire with low resistance
For low resistance
Thick wire
Lower temperature
Shorter wire

12. 9. Ohm’s Law Increasing resistance causes the current to decrease
Decreasing resistance causes the current to increase
Current equals the voltage difference divided by the resistance