1. Current Electricity and Circuits

2. What is electricity? Electricity is a form of energy
Electricity can exert a force on other objects
Think of your Laws of Charge activity
Curent Electricity is when electrons flow

3. How do electrons flow? Electrons are held very loosely by the nucleus.
This means an outside force that ‘pushes’ the electrons can cause them to move from one atom to another
The resulting effect is electricity.

4. Conductors and Insulators
We already know some materials can move electrons better than others
Think of static electricity-some materials lost electrons easier because their electrons can move more easily.
Materials that move electrons easily are called conductors
These materials have the physical property of being electrically conductive
Hold electrons loosely
Typically metals
Materials that do not move electrons are called insulators
These materials are not electrically conductive
Hold electrons tightly
Typically non-metals

5. Energy All Energy has to follow the 1st Law of Thermodynamics
“Energy Cannot Be Created or Destroyed, Only Transformed from One Form Into Another”
Since electricity is energy, it means we can’t ‘make’ electricity
We can change other forms of energy (heat, light, motion, etc) into electricity

6. Static Electricity
In static electricity, we saw electrons flow from one object to another
This electricity built up on the surface
It didn’t move through the material (that’s why it’s called static)
Current electricity is when electrons flow through a material.
Current electricity has a continuous flow of electrons
Current electricity is what we use to power our homes,
run our electronics, etc.

7. Current Electricity
Current Electricity is what is typically thought of as the most useful type of electricity
It is what powers our homes, what is created by batteries, and is what we typically use in everyday life.
This is because it is easy to change current electricity into useful forms of energy
Electrical energy is not useful on its own
Except for things like tasers and electric fences
Electricity is very useful when we convert electrical energy into light heat or motion

8. Voltage
Voltage is the energy per unit of charge. So what does that actually mean?
You can think of voltage as if it were the amount of ‘push’ that is given to electrons.
Voltage gives electrons energy to move
Measured in Volts (V)
𝑉= 𝑊 𝑄 Therefore 1 V= 1𝐽 1𝐶

9. Voltage
As you give electrons a push to the next atom, it leaves a positive charge behind.
The electrons (negatively charged) are attracted to the positive charge that was left behind.
Electrons keep moving towards the positive because they are attracted

10. Voltage The higher the voltage, the more push
This is why more volts makes lights look brighter, heaters hotter, etc.
Voltage is a lot like pressure (how much push you give water)
Good conductors don’t need much voltage to move electrons because their electrons are held loosely
They need less push to move
Insulators need huge amounts of voltage to move electrons because their electrons are held tightly
They need a lot of push to move

11. Current
Current in a river measures how much water passes in a given unit of time.
Electric current (I) is similarly measured by the rate of flow of charge in a given unit of time.
This depends on the properties of the material the electrons will move through and on the voltage.
More volts means more current
Better conductors mean more current
Current is a lot like the flow of water
Measured in Amperes, sometimes called amps. (A)
It is basically the amount of electrons that move through a spot in 1 second.
𝐼= 𝑄 𝑡 Therefore Ampere = 1𝐶 1𝑠

12. Circuits
So that is what is need to make current electricity…well almost. It isn’t good enough just to have electrons being pushed. They have to have somewhere to go.
Electricity must have a complete circuit in order to flow.
A circuit is a closed loop that allows for electrical current to flow.

13. Circuits
So that is what is need to make current electricity…well almost. It isn’t good enough just to have electrons being pushed. They have to have somewhere to go.
Electricity must have a complete circuit in order to flow.
A circuit is a closed loop that allows for electrical current to flow.

14. Circuits
Proper electric circuits require 4 parts Source: A device that delivers a potential difference (push) to drive the circuit. E.g. battery, cell, power supply. Conductor: A device that allows electricity to flow connecting all the parts of the circuit. E.g. copper wire. Control: A device used to open or close the circuit. E.g. switch or circuit breaker. Load: A device used to convert the electrical potential energy into another form of energy. E.g. light bulb, heater, motor.

15. Electric Circuit Conductor Conductor Power Source Conductor Control
Load

16. Loads and Resistance
Although a circuit can just be a power source and a path, there isn’t really a whole lot of point to that. Why not make that electricity do something?!
Electricity is used by adding a load to a circuit. A load is a object that converts electrical energy into:
Light
Heat
Sound
Motion
Loads have a property called resistance.
Resistance is how much the electric current has to push against
It is kind of like how much friction the electrons experience
Things that use electricity (like a light bulb) have higher resistance because they use electrical energy

17. Circuit Diagrams Circuits are really messy to look at in real life
Circuits are represented on paper with a circuit diagram
It is a quick sketch that shows all of the part of a circuit
Always has square corners and the different parts of the circuit are connected with a line

18. Circuit Diagrams
Circuit diagrams make electrical wiring easier to understand They have a universal code of symbols so that no matter what language you speak, people can understand how the circuit is made

19. The Power Source Each circuit must have a power source
The power source provides voltage to the circuits
Without one, the electrons would have no push. Without a push there is no current
There are 2 main types of power sources:
DC – Direct Current – Electrons flow in 1 direction
AC – Alternating Current – Electrons flow both directions

20. Direct Current
Direct Current (DC) is where electrons flow in 1 direction in a circuit
Electrons always flow from negative to positive
DC power sources are things like batteries and solar panels
They get the following symbols:
Cells (batteries)
Short line is negative
Long line is positive
DC Power Sources
Solar panels

21. Alternating Current
Alternating Current (AC) is when electrons flow both directions in a circuit
It is impossible to know which direction electrons are moving at any time
AC power is made by generators and is what come out of our outlets (plugs or sockets)
AC Power Sources get the following symbol in circuit diagrams:

22. Examples
Draw arrows around the circuit to show which direction the electrons are moving in circuits

23. What Energy ‘Looks’ Like Circuit Diagram Symbol
The Load
Type of Energy Made
What Energy ‘Looks’ Like
Circuit Diagram Symbol
What Goes in Circuit
Light Energy
Light
Light Bulb
Heat Energy
Heat or Warmth
Resistor
Sound Energy
Sound or Noise
Speaker
Mechanical Energy
Motion or Movement
Motor
The load in a circuit transforms electrical energy into a different type of energy
We then use this energy for many different applications

24. Circuit Diagram Symbols You Must Know
Other Important Symbols
Switch
Voltmeter
Ammeter
Connecting Wire
Loads
Label these Loads
Resistor
Speaker
Light
Motor
Power Sources
Label these Power Sources
Cell (batteries)
Direct Current
AC Power Source

25. Circuits to Schematics

26. Examples Draw a circuit with a DC power source and a light bulb
Draw a circuit with an AC power source, 1 resistor, and 1 motor
Draw a circuit with a 2 cell battery, 1 speaker, 1 light, and 1 resistor

27. Series and Parallel Circuits
There are two types of circuits that can be made
Series Circuit
All of the objects in the circuit are connected one after another
The electricity has only one path to take
Parallel Circuit
The electricity has more than one path to take in the circuit

28. Series Circuits The electricity has no options in a series circuit
It must travel through 1 path
In the example below, the electricity must go through every single light bulb before it gets back to the battery
This example has 3 lights in series

29. Parallel Circuits
When a circuit is parallel the electricity can take more than one path
Electricity takes different paths at nodes
In the example to the right, there are 3 lights, each in parallel

30. Examples
Say if the circuits below are in series or in parallel

31. Drawing Examples
Draw a circuit with an AC power source and a motor and light bulb in series
Draw a circuit with a DC power source and a speaker and resistor in parallel
Draw a circuit with a 3 cell battery, a light and motor in series, and a speaker in parallel to the light.

32. Combination Circuits
Circuits can have a combination of both series and parallel
What does the circuit above have?
The circuit above has:
-R3 parallel to R2
-R1 and R2 in series
-R1 and R3 in series