Lesson Summary In this lesson, students use an electromagnet coil and a switch to investigate ways to make the compass they built in Lesson 5 spin like a motor.  They review the concept of magnetic attraction and repulsion and examine once again the usefulness of on/off switching.  Both of these ideas are needed to understand the electric motors that students will experiment with in Lesson 13 and 14. Teacher Background The electric motor is used in a great number of modern electric appliances.  Motors use electromagnetism to convert electricity into mechanical work.  The work that motors perform is often work that people used to perform. The idea behind an electric motor is straightforward.  The basic ingredients are electricity, magnetism, and a way to turn the electricity on and off at the right time.  By turning on and off the electricity flowing to an electromagnet at the right moment, the electromagnet can be made to attract (when the switch is on and the electricity is flowing), then coast (when the switch is off). However, many commercial motors are designed to switch the direction of the electric current, making the electromagnet alternatively attract, then repel.  This is more efficient and enables the motor to run more smoothly.  If you or one of your students were to take apart a motor from an electric appliance, you probably would not find any permanent magnets.  This is because the motors in most appliances use electromagnets (coil) instead of permanent magnets.  These motors use electrical current from a wall outlet to operate, rather than current from a battery.  A number of ingenious ways have been devised to switch the electromagnets in motors on and off automatically, but the purpose of the motor is unchanged: to use electricity and magnetism to turn the shaft so that the motor can be used to do work. The motor in this lesson does not have an automatic switch-the switch is operated at the proper moment by the students.  It is constructed form an electromagnetic coil and the straw compass the students constructed in Lesson 5.  The motor could be used to do a small amount of work, but its real purpose is to demonstrate how a motor works. Set-up/Management Tips Make copies of Activity Sheet 5 for the whole class. For each group, make a transparency of Activity Sheet 5. Overhead markers will also be needed. Optional materials include poster board or big paper for each group to present their results. You may need to review how to construct a graph. Decide how you plan to conduct this “conference”. It can be small or elaborate, depending on the amount of time you would like to spend. This is nice time to incorporate art into the unit if you have the time to spend. Prepare the materials for distribution.  You may want to have some students help cut and coil the 1.5-meter wires around their hands, then strip the insulation off the ends.  The wire stripping procedure described in Appendix E may be used. Literacy Support Students should also make sure they write at least a few sentences in their science notebooks describing what the graph shows.   See the Student Activity Book for Lesson 11. Scientific Vocabulary The following words are key vocabulary words that will be introduced in this lesson and reinforced throughout the unit: No new vocabulary introduced this lesson.