1. Learning Objectives
I can describe electromagnetism, solenoid, and how they work.
I can explain how a magnetic field can make an electric current through induction.
I can explain how induction is used in generators.
I can describe transformers and how they are used.

2. Ohio New Learning Standards for Science
Ohio 8th Grade, Physical Science #1 (8.PS.1) – Forces between objects act when the objects are in direct contact or when they are not touching.

3. Lesson Opener   
The electromagnet is more powerful than a bar magnet & runs on electricity.
bringing someone into an organization
production of electric current from magnetism

4. Unit 7, Lesson 5 – Electromagnetism
What is electromagnetism?
- electromagnetism results when electric currents and magnetic fields interact with each other
- physicists discovered that electric currents produced magnetic fields
- the direction of the electrical current affects the magnetic field

5. Unit 7, Lesson 5 – Electromagnetism
- current in one direction caused the compass needle to move clockwise & current in the other direction caused it to move counterclockwise

6. Unit 7, Lesson 5 – Electromagnetism
How can you make a magnet using current?
- electric current in a single loop of wire produces a weak magnetic field
- much more powerful magnets can be made by making a solenoid or an electromagnet
solenoid
electromagnet

7. Unit 7, Lesson 5 – Electromagnetism
- a coil of wire that carries an electric current, and therefore produces an electric field, is called a solenoid
- the more loops in the solenoid, the stronger the magnetic field!
- the magnetic field is very similar to that of a bar magnet

8. Unit 7, Lesson 5 – Electromagnetism
solenoid

9. Unit 7, Lesson 5 – Electromagnetism
solenoid magnetic field

10. Unit 7, Lesson 5 – Electromagnetism
- wrapping a solenoid around an iron core makes an electromagnet
- this combines the magnetic field of the solenoid with the magnetic field of the iron core
- increasing the strength of the magnet can be obtained by adding more loops to the solenoid or increasing the electrical current!

11. Unit 7, Lesson 5 – Electromagnetism

12. Unit 7, Lesson 5 – Electromagnetism

13. Unit 7, Lesson 5 – Electromagnetism
Complete #6, pg.457

14. Unit 7, Lesson 5 – Electromagnetism
It makes a weak magnet stronger!

15. Unit 7, Lesson 5 – Electromagnetism

16. Unit 7, Lesson 5 – Electromagnetism
What are some uses for electromagnets?
- electromagnets are used for doorbells, hair dryers, speakers, particle colliders, Maglev Bullet Trains, & MRI scanners
Large Hadron Collider, Switzerland

17. Unit 7, Lesson 5 – Electromagnetism
- electromagnets are also used in galvanometers to help measure the strength & direction of an electric current
Complete #7, pg.458
galvanometer

18. Unit 7, Lesson 5 – Electromagnetism
When current is switched off, the magnetic force disappears and the metal can be released.

19. Unit 7, Lesson 5 – Electromagnetism
How do motors work?
- one of the most common places to find an electromagnet is in a motor
- an electric motor changes electrical energy (AC or DC) into mechanical energy
- simple motors have a coil or a loop of wire called an armature mounted between the poles of a magnet

20. Unit 7, Lesson 5 – Electromagnetism
- the armature becomes an electromagnet when current passes through it!
- the movement of the armature is caused by the poles creating pushes and pulls against one another
- the armature turns until its north pole is opposite the magnet’s south pole
- then, a device called a commutator reverses the direction of the current in the wire, causing the armature to complete its turn!
Complete #11, pg.460 & #12, pg.461

21. Unit 7, Lesson 5 – Electromagnetism
Ferris Wheel, carousel, car ride, Bumblebee ride
Both contain an electromagnet that rotates between the poles of another magnet.

22. Unit 7, Lesson 5 – Electromagnetism
What are some uses for induction?
- using a magnetic field to create an electric current in a wire is called electromagnetic induction
- magnets can make electric charges move inside of coiled wire
Complete #13 & #14, pg.462

23. Unit 7, Lesson 5 – Electromagnetism
1. Move the magnet or the coil faster.
2. Increase the number of loops in the coil.
The current would drop to zero!

24. Unit 7, Lesson 5 – Electromagnetism
- an important device that relies on electromagnetic induction is called a transformer, which uses induction to increase or decrease the voltage of AC
- transformers increase voltage to send it miles away and then decrease it for a single home

25. Unit 7, Lesson 5 – Electromagnetism
Power Plant Transformer

26. Unit 7, Lesson 5 – Electromagnetism
- the current in the wire on the primary side makes an electromagnet
- because the current alternates (AC), the magnetic field changes, which induces a current in the wire on the secondary side!

27. Unit 7, Lesson 5 – Electromagnetism
Which type of transformer is outside your home on the power lines: step-up or step-down transformer?
Answer: Step-Down Transformer
Complete #16, pg.463

28. Unit 7, Lesson 5 – Electromagnetism
500 volts = X volts
1,500 turns turns
500 x 600 = 300,000
300,000 ÷ 1,500 = 200
X = 200
Answer: 200 volts

29. Unit 7, Lesson 5 – Electromagnetism
- most of the electricity we use everyday comes from electromagnetic induction
- electric generators use induction to change mechanical energy into electrical energy
- power plants use mechanical energy from falling water (dams), wind, steam, ocean tides/waves and solar rays to generate electricity
Hoover Dam, Nevada/Arizona

30. Unit 7, Lesson 5 – Electromagnetism
- generators induce electric current when a magnet moves in a coil of wire or when a wire moves between the poles
- in a simple generator, a wire loop at the end of a rod moves through the magnetic field of a magnet
- alternating current (AC) is created by moving wire through a magnet in alternating directions
Complete #18, pg.464

31. Unit 7, Lesson 5 – Electromagnetism
Complete #18, pg.464

32. Unit 7, Lesson 5 – Electromagnetism
They are opposites!
Complete #19, pg.465

33. Unit 7, Lesson 5 – Electromagnetism
The interaction between
electricity & magnetism.
doorbell
industrial electromagnet
particle accelerator
MRI machine
galvonometer
Using a magnetic field to create an electric current.
transformer
generator

34. Visual Summary       

35. Exit Question
Describe how you could use a motor in reverse to generate electricity.
You could manually turn the armature of a motor. Electricity would be produced in the wire because moving a wire inside a magnet produced electric current!