1. Electric Current and Ohm’s Law

2. Electric Potential Energy(EPE)
Particles with charges have potential energy.
Opposite charges are attracted to each other.
Like charges are repelled.

3. Electric Potential Energy (EPE)
When two opposite charges are held apart, electric potential energy is present

4. Electric Potential Energy (EPE)
When two of the same charges are pushed together, potential energy is present.

5. Unit of Electric Potential (Voltage)
The unit of electric potential is volts.

6. What is an electric current?
An electric current is the flow of charged particles.
Particles always move from areas with many charged particles to areas with very few charged particles.

7. What is an Ampere (A)? An ampere is the unit of electric current.
Nearly always called an amp
1 ampere = 1 coulomb of charge every second
1 ampere = 1 coulomb/second

8. What causes an electric current?
A difference in energy potential (volts) causes charged particles to flow
The current will continue to flow until the volts are equal.

9. How can a current continue flowing?
A current can continue to flow as long as the voltage difference remains.
Batteries and generators create a voltage difference that allow current to flow.

10. Two types of current: Direct current: Alternating current:
All charge flows in one direction
Alternating current:
Charges reverse direction in a set frequency.

11. What is resistance?
Resistance is the property of a material that resists the flow of charged particles through it.

12. What is resistance measured in?
Resistance is measured in ohms.
The symbol Ω (omega) is used for ohms.

13. What affects resistance?
Conductivity
Better conductors offer less resistance
Temperature
Higher temperatures = higher resistance

14. What affects resistance?
Thickness of the wire
Thin wires have less resistance
Length of the wire
The longer the wire, the more resistance.

15. What is Ohm’s Law?
For a circuit of a given resistance, the current and voltage are proportional.

16. Ohm’s Law formula Current = voltage ÷ resistance
In units: amperes = volts ÷ ohms

17. Associated Formulas Voltage = current x resistance
Resistance = voltage ÷ current

18. Sample Problem One:
A 4V battery is attached to a circuit with 2Ω resistance. What is the current?
Current = voltage ÷ resistance
Current = 4V ÷ 2Ω
Current = 2A

19. Sample Problem Two:
A 5A current is occurring across a 3Ω resistor. What is the voltage?
Voltage = current x resistance
Voltage = 5A x 3Ω
Voltage = 15V

20. Sample Problem Three:
A 20V source is producing 4A of current. What is the resistance?
Resistance = voltage ÷ current
Resistance = 20V ÷ 4A
Resistance = 5Ω