Mathematics Grade Prototype Curriculum Guide

Objectives

The students should be able to

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  create a diagram of a magnetic field using a magnet;
  
• 
  compare and contrast a permanent magnet and an electromagnet;
  
• 
  explain how electricity is generated by a moving magnetic field;
  
• 
  construct a simple electromagnet, using a wire, nail, or other iron-bearing object, and a dry cell;
  
• 
  design and perform an investigation to determine the strength of an electromagnet.
  

Materials needed

For each group:

• 
  Bar magnets
  
• 
  Iron filings
  
• 
  Plastic baggies
  
• 
  50 to 75 cm insulated copper wire
  
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  1 nail
  
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  5 to 10 paper clips
  
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  2 “D” batteries (with rubber bands)
  
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  2 conducting strips
  
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  Scissors
  

Instructional activity

Content/Teacher Notes

Magnets are materials that will attract objects made of iron, steel, cobalt, and nickel. Many scientists believe that magnetism is due to the spinning movement of electrons as they travel around the nucleus of the atom. Each electron acts as a magnet. Non-magnetic materials have atoms in which half the electrons spin in one direction and the other half spin in the opposite direction. This cancels their magnetic effect. In atoms of magnetic materials, more electrons spin in one direction than in the other. This leaves each atom with a slight magnetic pull. These magnetic atoms group together in large clusters, called “domains.” These domains line up so that all of the north-seeking poles face one direction and all the south-seeking poles face the other.

The following Web site contains an explanation of magnetism with some diagrams that may be helpful to students: http://www.wcsscience.com/magnet/magnetism/page.html.

Materials can be made magnetic by exposing them to one of two things: a magnet or an electric current. When current flows through a wire it creates a magnetic field surrounding that wire. If a material that can be magnetized is placed into this field, it will become magnetic. When the electric current is turned off, the magnetic field is also ended, and the previously magnetized material will slowly revert to a non-magnetic state.

Soft iron is used as the core of electromagnets because it is magnetized quickly and it easily loses its magnetism when removed from the current. Electromagnets can be made stronger by increasing the number of turns of wire around the core or by increasing the current flowing through the wires.

One of the most dramatic examples of the use of an electromagnet is in salvage. Incredibly strong electromagnets are used to pick up metal objects to be moved. When the object, such as an entire car, has been moved, the current is shut off and it falls from the magnet.

Introduction

1. Ask the students what they know about electricity. Then ask them about magnets: How do we use magnets? Has anyone heard of an electromagnet? What does an electromagnet do?

2. Tell the students that today they will use the magnetic field around a wire to create an electromagnet, using layers of wire and a battery. Ask them what they think will happen. Give them a few minutes to discuss this question in groups and make a group prediction.

Procedure

1. Distribute permanent bar magnets in baggies to groups of students.

2. Provide iron filings for each group, and have students pour them over the magnet to visualize the magnetic field of the magnet.

3. Have students draw a diagram of the magnetic field in their science journals.

4. Distribute the materials for the electromagnet (nail, copper wire) to each group. Have each group tightly wrap the wire around the nail, starting at the nail point and making sure that about 8 cm of wire is left free at the end.

5. When they have wrapped the wire up the length of the nail all the way to the tip, have them start another layer on top of the one just completed.


6. When the second layer has completely covered the first, have students cut the wire so that about 10 cm is left free. Have them use scissors to strip the insulation from the last 3 cm of the wire.

7. Have students connect one loose end of the wire to a conducting strip that is connected to a battery terminal. Touch the other loose end to a conducting strip attached to the other battery terminal and then bring a paper clip close to the nail point.

8. Have students try to pick up more paper clips.

Safety Note: When touching the wire to the conducting strip, students should not touch the bare portion of the wire. The current being used is low and not dangerous, but the wire will heat up. It is also important that students not keep the circuit connected too long.

Observations and Conclusions

1. Ask the students how they think the electromagnet can be strengthened. If they have difficulty with the idea, suggest more batteries, another layer of wire, or another material instead of iron. Have each group decide which idea they would like to test and allow them time to do so. Remember to have them write in their journals what they have decided to test and their results.

2. Demonstrate for the student a stronger electromagnet. Let each group examine the magnet and draw conclusions about how it was strengthened.

3. Ask students why it is useful to have a magnet that can be turned on and off. Electromagnets are in doorbells, speakers, telephones, and almost every motor, but many people do not understand how such everyday devices work.

Sample Assessment

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  Assess student journals.
  
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  Have students find an electromagnet in an everyday machine or gadget and explain in their science journals where it is and what it does.
  

Resources

• 
  Connections: Connecting Books to the Virginia SOLs. Fairfax County Public Schools and The College of William and Mary. http://www.fcps.edu/cpsapps/connections. Presents a database of more than 1,000 works of children’s literature and their connection to the Virginia Standards of Learning.
  
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  How Stuff Works. http://science.howstuffworks.com/electromagnet.htm.
  
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  Outstanding Science Trade Books for Students K–12. National Science Teachers Association (NSTA). http://www.nsta.org/ostbc.
  
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  Science Education. Jefferson Lab. http://education.jlab.org/.
  
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  Search for Literature: Literature for Science and Mathematics. California Department of Education. http://www.cde.ca.gov/ci/sc/ll/ap/searchlist.asp. Offers a searchable database.
  

Static Electricity

(A revised version of an activity included in the Educator’s Guide from the NASA SciFiles program “The Case of the Electrical Mystery.” Used by permission.)

Organizing Topic Investigating Electricity

Overview Students investigate the properties of static electricity.

Related Standards of Learning 4.3c