1. EQ: What is electric current and how does it flow?
Electric Charges and Fields

2. Can You Move It?
Place the empty aluminum can on its side on your table
Have someone without a lot of product in their hair rub the balloon back and forth on their hair.
Hold the balloon 2-3 cm from the can.
What happens?
Move the balloon to the other side of the can.
What can we infer from our observations?

3. Static Electricity and Static Charges
You are in a hurry to get dressed for school, but you can’t find one of your socks.
You head for a pile of clean laundry.
You sort through it, but where is a sock that matches?
There it is! It’s sticking to a blanket.
What makes clothes and blankets stick together?
The explanation has to do with tiny electric charges.

4. Electric Charge
If you recall, the charged parts of an atom are the electrons and protons.
Protons have a positive charge (+)
Electrons have a negative charge( -).

5. Electric Charge
When two protons come close together, they push one another apart, or repel each other.
If two electrons come close together, they also repel each other.
Why?
Charges that are the same repel each other.

6. Electric Charge
The names positive and negative to describe electrical charges were given by Ben Franklin in the 1700s.
Electrical charges behave in specific ways, and can exist alone.
A negative charge can exist without a positive charge and vice versa, unlike magnetic charges (which we will get to soon!)

7. Electric Charge
If a proton and electron come close together, they attract one another.
Why do protons repel protons but attract electrons?
The reason is that they have different types of electric charges.
Opposite charges attract each other.

8. Drawing Conclusions Tear the paper into small pieces.
Have someone without a lot of product in their hair run the balloon through their hair several times.
Place the balloon close to, but not touching the paper.
What happens?
What can we conclude about the electric charges on the balloon and tissue paper?

9. Electric Forces We know that a force is a push or pull.
For example, the force of gravity pulls us toward the ground.
In electricity, electric force is the attraction or repulsion between electric charges.

10. How Electrical Charges Behave- Electric Fields
An electric field extends around a charged object.
An electric field is a region around a charged object where the object’s electric force is exerted on other charged objects

11. How Electrical Charges Behave– Electric Fields
When one charged object is placed in the electric field of another charged object it is either pushed or pulled.
It is pushed if they have the same charge
It is pulled if they have different charges

12. How Electrical Charges Behave– Electric Fields
An electric field is invisible
The strength is related to the distance from the charged object
The greater the distance, the weaker the field.

14. What is electric current, and how does it flow?
How Electrical Charges Behave – Static Electricity and
Static Discharge

15. How Electrical Charges Behave -- Static Electricity
Most objects have no overall charge, they are neutral.
Each atom has an equal number of protons (+) and electrons (-).
Each positive charge is balanced by a negative charge.
This results in an overall neutral charge.

16. How Electrical Charges Behave– Static Electricity
Some objects however, can become charged.
Protons are tightly bound in the nucleus of an atom
But electrons, moving in the shells surrounding the nucleus can sometimes leave their atoms.

17. How Electrical Charges Behave– Static Discharge
Objects that their electrons now has more protons (+) and will have a positive charge.
Objects that gain an electron (-), now has a negative charge.

18. How Electrical Charges Behave– Static Discharge
Static means not moving or changing
It is the build up of charges on an object.
An object is either negatively charged or positively charged.
In static electricity, charges build up but the charges do not flow continuously.

19. Static Discharge
When a negatively charged object and a positively charged object are brought together, electrons transfer until both objects have the same charge.
This loss of static electricity as electric charges transfer from one to another is called static discharge.

20. Static Discharge Lightning is an example of static discharge.
Lightning is a huge spark.
During a thunderstorm, air swirls and water droplets in clouds become electrically charged.

21. Static Discharge
Charges that build up as static electricity don’t move much, but they also do not stay there forever.
Electrons tend to move, returning to the object with the neutral condition.

22. Static Discharge
To restore a neutral condition in the clouds, electrons move from an area of negative charge to an area of positive charge.
This transfer causes a huge spark.
We see this spark as lightning

23. How Electrical Charges Behave– Transferring Charges
An object becomes charged only when electrons are transferred from one location to another.
Charges are neither created nor destroyed, they are transferred, this is called the Law of Conservation of Charge
If one object gives up electrons, another object gains electrons

24. https://www. youtube. com/watch
(bill nye static electricity)

25. Transfer of Charges

26. How Electrical Charges Behave– Transferring Charges
There are three methods by which charges can be transferred to build up static electricity:
Charging by friction
Charging by conduction
Charging by induction

27. How Electrical Charges Behave– Transferring Charges: Friction
Charging by friction is the transfer of electrons from one uncharged object to another by rubbing.
Opposite charges attract, causing objects to “stick” together.
EX:
Walking on carpet in socks.
Brushing your hair
Clothes sticking together in the dryer

28. How Electrical Charges Behave– Transferring Charges: Friction
When two uncharged objects rub together, some electrons from one object can move onto the other object.
The object that gains electrons (-) becomes negatively charged
The object that loses electrons becomes positively charged.

29. Charging by Friction Place the balloon next to someone’s hair
What happens?
Why is the balloon not attracted to the hair?
How could we put a negative charge on the balloon?
Have someone without a lot of product on their hair rub the balloon on their hair.
What happened?
Why?
Why will the charge lose strength over time?

30. How Electrical Charges Behave– Transferring Charges: Conduction
When a charged object directly touches another object, electrons can be transferred between the objects.
Electrons will transfer from the object that has more electrons to the object with less electrons

31. How Electrical Charges Behave– Transferring Charges: Conduction
Charging by the transfer from a charged object to an uncharged object by direct contact
Ex: “shocking” someone you touch
Your sock touching your foot and carrying the charge

32. How Electrical Charges Behave– Transferring Charges: Conduction
EX:
Putting on the negatively charged due to friction sock on your foot.
The negatively charged sock touches your skin and electrons are transferred to you by direct contact.
“Shocking” someone when you touch them

33. How Electrical Charges Behave– Transferring Charge: Induction
When charging by friction and conduction, electrons were transferred when the objects touched.
However, when charging by induction, objects do not touch.

34. How Electrical Charges Behave– Transferring Charge: Induction
Charging by induction is the movement of electrons to one part of an object that is caused by the electric field of a second object.
The electric field attracts or repels electrons in the second object.
No contact is necessary.
Ex:
Getting “shocked” when you go to touch something metal, but made no actual contact.

35. Detecting Electric Charges
Electric charges are invisible.
They can be detected by an electroscope.
When the electroscope is uncharged, the metal strips hang down.
When a charged object is detected, the metal leaves repel each other.
You cannot use an electroscope to determine if a charge is positive or negative.

36. What is electric current, and how does it flow?

37. Electric Current
Lightning releases a large amount of electrical energy.
But the electric charge from lightning can’t be used to power a TV, a video game, or the classroom lights.
Why?
Lightning releases its electrical energy for an instant (static discharge), and electric devices need electric charges that flow continuously.
They need electric current

38. Electric Current
Static charges like lightning, do not flow continuously.
But when electric charges are made to flow through a wire or similar material, they produce an electric current.

39. Electric Current
Electric current is the continuous flow of electric charges through a material.
The amount of charge that passes through the wire is the rate of electric current.
The unit for measuring the rate of electric current is called the Ampere, or Amp, for short.
The number of amps describes the amount of charge flowing past a given point each second.

40. Electric Current Watch this short clip:
How were the chocolates like electric current?
When was the current the fastest?
When was the current slowest?
What is the unit of measurement to describe the rate of the current?

41. Electric Current
Electric current does not automatically exist in a material.
Current requires a specific path to follow. To produce electric current, charges must flow from one place to another.

42. Electric Circuit
An electric circuit is a complete, unbroken path through which electric charges can follow.
The cars on the racetrack are like the charges on a racetrack.
If the racetrack follows a continuous loop, the cars can move around the racetrack continuously.
However, if a piece of the racetrack is missing, the cars will be unable to move around the loop.

43. Electric Circuit
If the circuit is complete, charges can flow continuously.
If an electric circuit is broken, charges will not flow.
EX: Lamp
Plugged in: complete circuit
Unplugged: incomplete circuit

44. Conductors and Insulators
Charges will flow easily through a circuit made of metal wires.
But what about plastic?
Electric charges do not flow easily through every material.
A conductor transfers electric charges well.
An insulator does not transfer electric charges well.

45. Conductors and Insulators
A material through which electric charge can flow easily.
EX: copper, silver, iron
Atoms contain loosely bound electrons, which form an electric current when moving through a conductor
A material through which electric charges do not flow easily.
EX: wood, plastic, cloth, sand
These are used to stop the flow of charges

46. What is electric current and how does it flow?
Electric Circuits

47. Electric Circuits
It’s a clear, cold night as you stroll along the river with that special someone.
The city is brightly lit, and the water in the river sparkles brightly.

48. Electric Circuits
In addition to the lights on the lamp posts, a string of lights borders the river path.
As you walk, you notice that a few of the lights in the string are burned out.
The rest of the lights burn brightly.

49. Electric Circuits You wonder….
If one bulb is burned out, how can the rest of the lights continue to shine?
The answer depends on how the electric current is designed.

50. Electric Current/Circuit: A Review
Electric current is the continuous flow of electric charges through a material.
An electric circuit is a complete, unbroken path through which electric charges can follow.

51. Features of a Circuit
All electric circuits have the same basic features:
Circuits have devices that are run by electrical energy
A circuit has source of electrical energy
Electrical circuits are connected by conducting wires.

52. Circuits are connected through conducting wires
A switch is often included in a circuit to control the current in the circuit.
Using a switch, you can turn a device on or off by closing or opening the circuit.

53. Circuits are connected through conducting wires
The conducting wires complete the path of the current.
They allow charges to flow from the energy source to the device that runs on the electric current and back to the energy source.

54. Circuits have devices that are run by electrical energy
A radio, a computer, a light bulb and a fan are all devices that transform electrical energy into another form of energy.

55. Circuits have a source of electrical energy
Batteries, generators, and electric plants all supply energy to circuits.
The source of electrical energy makes charges move in a circuit, allowing the device to do work.

56. Two Types of Electrical Circuits
There are two types of electrical circuits:
Series
Parallel

57. Series Circuits
All the parts of an electric circuit are connected one after another along a path
There is only one path for the current to take
For example, a switch and two light bulbs connected by a single wire form a series circuit.

58. Series Circuits
It is simple to design and build but it has some disadvantages.
If a bulb burns out, the circuit is broken and there is no other path for the current to take.
So if one light burns out, the other lights go out

59. Series Circuits
Also the bulbs will become dimmer as more bulbs are added
Bulbs are known as resistors.
When resistance increases, current decreases.
This increased resistance means that as bulbs are added, the string as a whole will burn less brightly

60. Parallel Circuits
As you gaze at a string of lights, you observe that some bulbs burn brightly, but others are burned out.
This observation is proof that the bulbs are connected in a parallel circuit.

61. Parallel Circuits
In a parallel circuit, the different parts of the circuit are on separate branches.
In a parallel circuit, there are several paths for current to take.
Each bulb is connected by a separate path from the battery and back to the battery.

62. Parallel Circuits
What happens is a light burns out in a parallel circuit?
If there is a break in one branch, charges can still move through the other branches.
If one bulb goes out, the others remain lit.
Switches can be added to turn lights off and on without affecting the other branches.

63. Parallel Circuits
When you add more branches in a parallel circuit, the resistance decreases.
In a parallel circuit, the electric current has more paths to follow, so the overall resistance decreases.

64. Parallel Circuits When resistance decreases, current increases.
The additional current travels along each new branch without affecting the original branches.
The brightness of the light bulbs does not change

65. Household Circuits
Series circuits are not practical in a home, office or school because if one electronic device stops working, all would cut off.
Parallel circuits are installed with switches to control the current flowing through the circuit.

66.
Alternative Energy Souurces