1. Unit 2 Electrical Quantities and Ohm’s Law
Objectives:
Define an ampere.
Define a volt.
Define an ohm.
Define a watt.

2. Unit 2 Electrical Quantities and Ohm’s Law
Objectives:
Compute electrical values using Ohm’s law.
Discuss basic types of circuits.
Use the Ohm’s wheel charts.

3. Unit 2 Electrical Quantities and Ohm’s Law
The ampere is a measurement of the amount of electricity that is flowing through a circuit.
One ampere (A) is defined as one coulomb of electricity flowing past a given point in one second.

4. Unit 2 Electrical Quantities and Ohm’s Law
There are two theories about current flow.
Electron flow theory describes current flow from negative to positive.
Conventional current flow theory states electrical current flows from positive to negative.

5. Unit 2 Electrical Quantities and Ohm’s Law
Conventional current flow theory and electron flow theory.

6. Unit 2 Electrical Quantities and Ohm’s Law
Electrons moving from atom to atom.

7. Unit 2 Electrical Quantities and Ohm’s Law
Electrical sources are divided into two basic types:
Direct Current (DC) which is unidirectional (one way).
   
Alternating Current (AC) which is bidirectional (two way, or back and forth).
   

8. Unit 2 Electrical Quantities and Ohm’s Law
A complete path must exist before electricity can flow through a circuit.
A circuit with a complete path for electrical flow is called a closed circuit.
If the circuit path is incomplete or broken, this is called an open circuit.

9. Unit 2 Electrical Quantities and Ohm’s Law
A simple switch closes and opens an electrical circuit.

10. Unit 2 Electrical Quantities and Ohm’s Law
A short circuit has an unintended shorter pathway.

11. Unit 2 Electrical Quantities and Ohm’s Law
A volt or voltage is electrical pressure.

12. Unit 2 Electrical Quantities and Ohm’s Law
An ohm is the unit of resistance or opposition to the flow of electricity.

13. Unit 2 Electrical Quantities and Ohm’s Law
The watt is the unit of electrical power.

14. Unit 2 Electrical Quantities and Ohm’s Law
Amperes times volts equals watts.

15. Unit 2 Electrical Quantities and Ohm’s Law
Common power units.

16. Unit 2 Electrical Quantities and Ohm’s Law
Ohm’s law states that in a DC (Direct Current) circuit, the current is directly proportional to the voltage and inversely proportional to the resistance.
E(volts) = I(amps) x R(ohms)

17. Unit 2 Electrical Quantities and Ohm’s Law
Ohm’s Law Symbols:
P is the symbol for Watts.
E is the symbol for Volts.
I is the symbol for Amperes.
R is the symbol for Resistance or Ohms.

18. Unit 2 Electrical Quantities and Ohm’s Law
Ohm’s Law states that it takes one volt to push one ampere through one ohm.
E = Volts
E = I x R
R = Resistance
I = Amps

19. Unit 2 Electrical Quantities and Ohm’s Law
Using the Ohm’s law chart.
E = I x R
I = E / R
R = E / I

20. Unit 2 Electrical Quantities and Ohm’s Law
Adding P (watts) to the Ohm’s law chart.
P = E2 / R
P = E x I
P = I2 x R
I =
I = P / E
I = E / R
R = E / I
R = P / I2
R = E2 / P
E =
E = I x R
E = P / I

21. Unit 2 Electrical Quantities and Ohm’s Law
Remember:
E = EMF, or voltage
I = intensity of current, or amperage
R = resistance in ohms
P = power in watts
E(volts) = I(amperes) x R(ohms)
P(watts) = I(amperes) x E(volts)

22. Unit 2 Electrical Quantities and Ohm’s Law
Review:
An ampere (A) is one coulomb per second.
Either the letter I, which stands for intensity of current flow, or the letter A, which stands for amperes, can be used in Ohm’s law formulas.

23. Unit 2 Electrical Quantities and Ohm’s Law
Review:
Voltage is referred to as electric pressure, potential difference, or electromotive force. An E or a V can be used to represent voltage in Ohm’s law formulas.
An ohm (Ω) is a measurement of resistance (R) in an electric circuit.

24. Unit 2 Electrical Quantities and Ohm’s Law
Review:
The watt (W) is a measurement of power in an electrical circuit. It is represented by either a W or a P (power) in Ohm’s law.
Before current can flow, there must be a complete circuit.
A short circuit has little or no resistance.

25. Unit 2 Electrical Quantities and Ohm’s Law
Review:
Before current can flow, there must be a complete circuit.
A short circuit has little or no resistance.