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.

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.

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

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

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

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

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

Unit 7, Lesson 5 – Electromagnetism solenoid

Unit 7, Lesson 5 – Electromagnetism solenoid magnetic field

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!

Unit 7, Lesson 5 – Electromagnetism

Unit 7, Lesson 5 – Electromagnetism

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

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

Unit 7, Lesson 5 – Electromagnetism

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

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

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

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

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

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

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

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!

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

Unit 7, Lesson 5 – Electromagnetism Power Plant Transformer

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!

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

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

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

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

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

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

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

Visual Summary       

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!