1. Circuits and Ohm’s Law

2. Flowing Electricity, Voltage
Work must be done to move a charged particle
The amount of work required to move a charge between two points (the work per unit charge) is called the electric potential difference between two points
The potential difference is measured in
Volts (V)

3. Electric Circuits
A Circuit is when a wire is connected to the terminals of the source to form a complete path that electrons can follow

4. Electrical Circuits
A Circuit is a closed conducting loop through which an electric current can flow.

5. Electrical Circuits - Parts
Source of Energy – battery, thermocouple, electric generator, photocell
Resistance (load) – device that uses energy – light bulb, appliance, machine, motor
Photocell - a solid-state device that converts light into electrical energy by producing a voltage, as in a photovoltaic cell, or uses light to regulate the flow of current, as in a photoconductive cell: used in automatic control systems for doors, lighting
Thermocouple - a kind of thermometer consisting of two wires of different metals that are joined at both ends; one junction is at the temperature to be measured and the other is held at a fixed lower temperature; the current generated in the circuit is proportional to the temperature difference

6. Electrical Circuits - Parts
Wires – serves as a path to conduct the electrons
Switch – opens (off) and closes (on) circuit
Photocell - a solid-state device that converts light into electrical energy by producing a voltage, as in a photovoltaic cell, or uses light to regulate the flow of current, as in a photoconductive cell: used in automatic control systems for doors, lighting
Thermocouple - a kind of thermometer consisting of two wires of different metals that are joined at both ends; one junction is at the temperature to be measured and the other is held at a fixed lower temperature; the current generated in the circuit is proportional to the temperature difference

7. Circuit Diagrams
Photocell - a solid-state device that converts light into electrical energy by producing a voltage, as in a photovoltaic cell, or uses light to regulate the flow of current, as in a photoconductive cell: used in automatic control systems for doors, lighting
Thermocouple - a kind of thermometer consisting of two wires of different metals that are joined at both ends; one junction is at the temperature to be measured and the other is held at a fixed lower temperature; the current generated in the circuit is proportional to the temperature difference

8. Circuit Diagram Symbols
Photocell - a solid-state device that converts light into electrical energy by producing a voltage, as in a photovoltaic cell, or uses light to regulate the flow of current, as in a photoconductive cell: used in automatic control systems for doors, lighting
Thermocouple - a kind of thermometer consisting of two wires of different metals that are joined at both ends; one junction is at the temperature to be measured and the other is held at a fixed lower temperature; the current generated in the circuit is proportional to the temperature difference

9. Types of Electrical Circuits
Series
All the parts of an electric circuit are connected one after another
Only 1 path for the electron to take

10. Series Circuit

11. Types of Electrical Circuits
Parallel
Different parts of an electric circuit on separate branches
Several paths for electrons to take

12. Parallel Circuit

13. Series Circuit
Disadvantage: if there is a break anywhere in the circuit, the entire circuit is open and no current can flow
Ex: cheap holiday lights

14. Series Circuit

15. Parallel Circuit
If there is a break in one branch, the electrons and current can still flow through the other branches
Ex: more expensive holiday lights
Your house is wired with parallel circuit

16. Parallel Circuit

17. Electric Current
A flow of charge (electrons) is called an electric current
letter variable = I (electric current)
The amount of charge that passes a given point per second
The unit for current is the ampere (A) or amp for short

18. Resistance to Flow Items in the circuit resist the flow of electrons
Load/appliance, lights, TVs
Wires
The current is slowed by interactions with the load and atoms in the wire
a property of a conductor by virtue of which the passage of current is opposed, causing electric energy to be transformed into heat:

19. Resistance to Flow Resistance Factors that affect resistance:
Letter variable = R
Unit = ohms (Ω)
Factors that affect resistance:
Resistance Increases with, longer wire
Resistance Increases with higher temperature
Resistance Decreases with a thicker wire
a property of a conductor by virtue of which the passage of current is opposed, causing electric energy to be transformed into heat:

20. Ohm’s Law
Ohm’s Law states the relationship between voltage difference, current and resistance in a circuit.
Ohm’s Law states that the current in a wire (I) is equal to the voltage (V) divided by the resistance (R)
I=V/R

21. Ohm’s Law Current (l) = amperes Voltage (V) = Volts
Resistance (R) = Ohms

22. V R I
Practice Problem 1
Calculate the voltage difference in a circuit with a resistance of 25 Ω if the current in the circuit is 0.5 A.

23. V R I
Practice Problem 2
Find the current in a circuit that has a voltage of 120 volts and a resistance of 60 Ω.

24. V R I
Practice Problem 3
Find the resistance of a circuit that has a voltage of 120 volts and a current of 4 amperes.