Electromagnetic Forces

Accessing Prior Knowledge I._Illuminate_APK_Electromagnetic_Forces 2016.pdf

Daily Science Question 1. What is a magnet? 2. What is magnetism? 1. A magnet is any material that attracts iron and materials that contain iron. 2. The attraction or repulsion of magnetic materials

Hook Activity Pre-Activity Discussion 1. What are two ways a magnetic field can be created? 1. By a magnet and by an electric current. 2. Electricity running through a single wire can generate a very weak magnetic field. How do you think a stronger electromagnetic field can be generated? 2. An electromagnetic field can be strengthened by coiling the wire and adding additional coils.

Post-Discussion Discussion 1. Why did the needle get sucked into the straw when the wire was connected to the battery? 1. Electric current from the battery passed through the wire and created a magnetic field. The magnetic force pulled the needle into the straw. 2. Is the electromagnet actually creating suction? 2. No, there is no movement of air. It is creating a magnetic field which attracts the needle. 3. This technology is called a solenoid. How might solenoids be useful in everyday life?

How do magnetic poles interact? Every magnet has two ends to it; north pole and a south pole. These ends are called a magnetic pole. What happens when you hold two magnets together? If you bring the north pole side near the south pole side, the two unlike poles attract one another. If you bring two norths, or two souths together they repel each other.

Magnetic Fields The area of magnetic force around a magnet is known as the magnetic field.

Magnetic Field Lines Magnetic Field lines are lines that map out the invisible magnetic field around a magnet. Spread out from one pole, curve around the magnet and return to the other pole. The lines never cross when they move from the North pole to the South pole. The closer together the lines are, the stronger the fields.

A Single Magnetic Field If you were to cover the magnet with iron filings, they will form a pattern similar to magnetic field lines.

Combined Magnetic Fields

What is Earth’s magnetic field like? How does a compass relate to our lesson on magnets? A compass is a device that has a magnet on a needle that spins freely. It is used for navigation because its needle points north. Why does this happen? Because Earth has a magnetic field around it and two magnetic poles.

Earth’s Core Earth’s core is a large sphere of metal that occupies Earth’s center. Two parts to the core: inner & outer parts The outer core is made of hot liquid iron The motion of this iron creates a magnetic field similar to the magnetic field of a bar magnet.

How are electric currents and magnetic fields related? Scientist Hans Christian Oersted discovered that the two were related by accident. When he was holding a compass near the wire, he observed that the compass needle changed directions and created a current in the wire

Oersted’s Experiment To further his investigation, he set up several compasses around a wire with no current and noticed that all the needles pointed North. Then, after he produced a current in the wire, the compass needles pointed in different directions to form a circle. He then concluded that the current had produced a magnetic field around the field.

Electric Current and Magnetism The relationship between electricity and magnetism is called electromagnetism

What is a magnetic field produced by a current like? The magnetic field produced by a current has a strength and a direction. The field can be turned on or off, have its direction reversed, or have its strength changed

How can you change all that? To turn a magnetic field produced by a current on or off, you just turn it on or off. To change the direction of the magnetic field, reverse the direction of the current There are 2 ways to change the strength of the magnetic field. 1. Increase the amount of current in the wire 2. Make a loop or coil in a wire

Electricity, Magnetism, and Motion What do trains, fans, microwave ovens, and clocks all have in common? All use electricity.

Energy and Motion We learned that magnetic forces can produce motion. Example when magnets move away or toward each other. The ability to move an object over a distance is called energy The energy associated with electric currents is called electrical energy. The energy an object has due to its movement or position is called mechanical energy.

Energy Transformation When a wire with a current is placed in a magnetic field, electrical energy is transformed into mechanical energy. This happens when the current causes the wire to move

Activity 1: Viewable Interactions Pre-Activity Discussion 1. If I draw magnetic force lines to diagram the magnetic field on this magnet, would the point end or the tail end of the arrow be on the north pole? 1. Tail end. (Draw a line of force starting at the north pole and curve it down and point it to the south pole.) 2. Would every magnetic line in this field show the same direction of force? 2. Yes. (Drawn in a few more, starting with tail at north and end with pointing to south.) 3. Do the force arrows show a north to south direction or south to north direction? 3. North to south. 4. Do you think any of the magnetic lines in this field of force would cross over each other? 4. Accept all answers, students will discover that they do not cross.

Activity 1: Discussion Post-Activity Discussion 1. Describe how your model system demonstrated the magnetic force strength in the field. 2. Did lines of force cross each other in your model system? Explain. 3. Were you able to visually see the polar direction of magnetic force in the lines of iron filings? 4. How did the iron filing patterns show attractive forces between magnetic poles? 5.How did the iron filing patterns show repulsive forces between magnetic poles? 6.Use the direction of magnetic force shown on your diagrams to explain why the magnetic fields repelled or attracted.

Review What is an electric current? A flow of electrical charges usually through a wire What is an electric circuit? The path in which an electric current flows What is an electromagnet? A magnet created by using electricity

Activity 2: Electromagnetism Pre-Investigation Discussion 1. What is an electric current? 1. A flow of electric charge usually through a wire 2. What is an electric circuit? 2. The path in which an electric current flows A closed circuit is required for electricity to flow. 3. What is an electromagnet? 3. Accept all answers, but lead students to look at the make up of the word - electro meaning electricity and magnet. An electromagnet is a magnet created using electricity.

Activity 3: Computer Simulation https://phet.colorado.edu/en/simulation/legacy/generator