Lesson 7: Electromagnetism

 

Essential Concepts:

There is fundamental connection between electricity and magnetism.

Electricity can be used to create magnetism

Moving magnets can be used to generated electricity

Electromagnets: construction and use

Simple Machines help us adapt to the world around us

 

Background:

 

Electromagnets

 

·      Electric current flowing through a wire produces a magnetic field around the wire

·      This field can be made stronger by wrapping the wire in a coil

·      This coil is called a solenoid. The area inside the solenoid is called the core

·      The magnetic field can be made even stronger by inserting a conductor into the core.

·      This whole contraption is called an electromagnet

 

Generators

·      Just as a current (which after all is just moving electrons) produces a magnetic field, a moving magnet produces an electric field.

·      Moving a magnet rapidly near a conductor creates a current in the conductor

·      This is how most electric generators work (most use steam power to spin a turbine which is connected to magnets. These magnets spin rapidly next to conducting wires and electricity is produced!)(wood, coal, oil and gas burning, and nuclear fission are used to produce steam – thermal uses natural steam from the ground – hydro and wind use water pressure from rivers and air pressure to directly spin the turbine)

 

Simple Machines (additional teacher background on simple machines will be required)

·      There are 6 types of simple machines: the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw

·      These simple machines can be combined to create complex machines

·       Some of the simple machines can be used in different ways. For example, a “first class” lever has a fulcrum in the middle, and can be seen in a scissors or a see saw. A “second class” lever has the weight to be moved in the middle of the lever and the fulcrum at the end, such as in a nutcracker or wheelbarrow. A fishing pole, broom, and golf club are all examples of the “third class” lever, which allows you to put effort between the fulcrum and the weight (load).

·      A fixed pulley (one that is attached to something) reverses the direction of the force needed to move an object.

 

Goal 1: Students will understand that electricity and magnetism are connected.

Goal 2: Students will design and build a device that uses an electromagnet, a pulley and a lever using the Engineering Design Process

 

Objectives:

Students will build an electromagnetic crane to temporarily lift metal objects

Students will successfully use a lever and a pulley in the construction of this crane

Students will create and communicate using the engineering design process

 

Materials:

 

Video/DVD “SchoolHouse Rock”

Class set pulleys

Small model of house              Cardboard base           small toy truck                        cardboard

Metallic item to be moved by students (T-pins, washers, etc..)

D batteries                  wirestrippers                          Wire                bolt or nail

Craftsticks                  tape                 old thread holders

Students will need:

Shoebox or cardboard to make box                            

 

 

Procedure:

 

Preclass setup:

 

Build a simple model of a house, perhaps out of a small milk carton. Put it on a flat cardboard base and make a little lawn around it. Take some form of metal that can be attracted by a magnet and make a “meteor”. An example might be several T-pins stuck into a crumpled up ball of paper or several washers wrapped in masking tape. This metal will be the “meteor” that has landed in your lawn. Be careful not to make the meteor too heavy. Test it yourself first with an electromagnet that you have made. Make a simple fence that is 5 or 6 centimeters tall. Park a toy truck near the fence. This cardboard base will be the testing area for the students to use after they have built their own electromagnetic cranes.

 

1. Show the schoolhouse rock videos: “Electricity” and “Energy”. Pause during the Energy video to discuss: How is electricity made? (electromagnetic turbine), what are the kinds of ways to make steam? (wood burning, coal burning, oil/gas burning, nuclear, thermal, also solar, wind, and dams) What are the problems with each?
• Wood—forests cleared, pollution
• Coal—heavy pollution, limited quantities
• Oil/gas—limited quantities, air and water pollution
• Nuclear—waste disposal, possible accidents
• Thermal—need place where earth’s crust is thin
• Solar—clouds, space for collectors, expensive, and making the collectors causes pollution
• Wind—need steady supply of wind(look at Cape & Islands controversy)
• Dams—need a large river(look at China: 3 Gorges area flooded for it)

 

Most of these types of generators use some form of stored energy (heat) to produce high pressure steam to turn a turbine. Wood, Coal, and Oil are burned to produce this heat, nuclear fission gives off a LOT of heat, and the heat of the Earth is used directly in Thermal. Wind and Hydroelectric use motion in nature (air and water) directly to turn a turbine. The turbine spins a lot of magnets rapidly, next to some conductors. The rapidly changing magnetic field of the spinning magnets induces a current in the conductors. Solar is the only type that skips the mechanical energy step, directly converting solar energy into electrical energy

 

 

 

2. Review how a generator works.
3. Make the connection: If you can use magnets to make electricity and electricity to make magnets, then it is possible to make a temporary magnet that only works while there is electricity.
4. Introduce students to a problem:

 

A meteor has crashed into your backyard, luckily missing your house. You do have a truck to take the meteor away, but the rock is too heavy to lift and you don’t want to disturb your garden by dragging it. You know that the meteor has metal in it.

You want the students to build a crane with an electromagnet to lift the meteor and deposit it into the back of the truck. The crane must be able to pull the meteor up over the fence and lower it into the truck. The electromagnet must be powerful enough to lift the object.

 

5. Define the problem as a design challenge. What information do they need to know about the problem in order to solve it? Does the color of the house matter? (no) What about the height of the fence? (yes)                                                     Try to define (identify) the problem. 1. Must pick up the meteor 2. Must swing the meteor so that it is above the truck 3. Must release the meteor. Diagram the problem on the board and write down the specific problems.
6. What will you need to know in order to solve the problem: Research the need. 1. The children will need to learn how to make an electromagnet. Most books on electricity or magnets contain the directions for building an electromagnet. If you do not have enough resources in the classroom, you may make copies of a design you like. 2.They will also need to design a structure that contains a pulley, a lever, and a rotating platform. What shapes might be stronger when building? What materials? What are the problems that might come up when building a structure like a crane? (Stability)
7. The students next need to Develop Possible Solutions. Use the diagram on the board to help them formulate their ideas. They need to put their own diagrams and list of materials into their lab notebook. They will need more than one solution. Perhaps come up with a list of objects that are common and that could be used for their crane designs. For example: tissue boxes, paper towel tubes, rubberbands, tape, string, cardboard, plastic water bottles(filled?), craft sticks, pieces of wood, etc..
8. Next they must Choose the Best Possible Solution. This could be the time when you decide to have the students work in teams to complete the design. One advantage to team work is that they will be able to combine resources and ideas. One problem is that you will have to wary of one person in the team monopolizing the process. You might want to let them decide on their final choices after they have been able to find materials at home.
9. After finalizing their design, the students must Construct a Prototype—they need to build it. New problems may come to light (“it keeps falling over”, “the wires are in the way”…) These problems need new design solutions.
10. Once they have a working prototype, they may bring it up to the testing area and Test and Evaluate the Solution. Again, new problems may occur. (“The fence is too high”, “The electromagnet is not strong enough”…) It is probably best to offer help to frustrated teams or individuals and all students may need to be informed of how to make a stronger electromagnet.(more coil, wrap the coil better, more voltage) If you have time, they can experiment on their own with: using more coils around the nail with more wire or increasing the voltage.
11. It is finally time to make sure that they get credit for their design. In order to do this, they must Communicate the Solution. This will require a final labeled diagram. If time permits, it would be enjoyable to have the students present their designs to the entire class.
12. Activities: discussion, diagram drawing, designing and building electromagnetic crane, diagramming final design

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The Design Process

The Electromagnetic Crane

1.   Try to Define (identify) the problem.

 

1.    Must pick up the meteor

2.    Must raise the meteor so that it is higher than the fence

3. Must swing the meteor so that it is above the truck

4. Must release the meteor.

 

2.   What knowledge will you need to know in order to solve the problem:

Research the need.

 

1.    Knowledge about electromagnets        : How do they work?    

2. Knowledge about pulleys and levers: What do they do and how do you use them?

         3. Knowledge about structures: What will make a structure sturdy and stable?

         4. Knowledge about materials: What materials are best for the job?

 

3. Develop Possible Solutions. What materials are available for your use? How will you use them? Can you think of more than one way to use the materials? Each member of the group must draw a labeled diagram of a solution to the problem that uses materials that are available to you.

4. Next you must Choose the Best Possible Solution. The group must form a consensus as to a final solution that combines the best elements of each member’s design.

5. After finalizing your design, you must Construct a Prototype —you need to build it. New problems may come to light (“it keeps falling over”, “the wires are in the way”…) These problems need new design solutions. Keep careful notes and diagrams of changes.

 

6. Once you have a working prototype, you may bring it up to the testing area and

Test and Evaluate the Solution.

Again, new problems may occur. (“The fence is too high”, “The electromagnet is not strong enough”…) You may have to go back to step 3 several times.

 

7. It is finally time to make sure that you get credit for your design. In order to do this, you

must Communicate the Solution. This will require a final labeled diagram.

 

 

Electromagnets                  Name____________________ Class _______

 

         These are the experiments you as a group need to complete in school before you can start on your final project. Have a classmate put his/her initials on the line after they have seen you successfully complete the experiment and than color in the O.

 

Unwrap 2 lengths of red enamel magnet wire, one about20 ft. long, and one 3 ft. long. Be very careful not to get your long wire tangled up! Carefully sand all of the enamel off of the last inch of both ends of each wire. You are going to make two magnets, one with each wire.

 

Very Important:

1.      Be sure to always wrap in the same direction (clockwise or anti-clockwise).

2.      Wrap neatly and tightly for the best results.

 

___O wrap the short wire around an iron nail and attach to a 1.5 V battery and a switch. How many paper clips can you pick up? ___

 

___O wrap the long wire around an iron nail and attach to a 1.5 V battery and a switch. Leave two feet of wire unwrapped on each end. How many paper clips can you pick up? ___

         Notes:

 

 

 

___O Increase the voltage to 3.0

Notes:

 

 

 

 

 

 

 

 

___O increase the voltage to 9.0

         Notes:

 

 

 

___O Sketch a diagram of your Final Project.