Protomotor. Category: Physics: Electricity & Magnetism. Type: Make & Take Rough Parts List: Tools: Drill Hot glue gun

Transcription

1 Protomotor Category: Physics: Electricity & Magnetism Type: Make & Take Rough Parts List: 1 Baseboard 1 Dowel 1 Pushpin 1 Penny 4 Magnets 1 Cup 1 Nail 1 Battery 1 Paperclip 1 Brass fastener Electrical wire Electrical tape Tools: Drill Hot glue gun Video: How To: Tape a pushpin onto the end of a dowel. Drill a hole in the center of the baseboard. The hole diameter should be slightly smaller than the diameter of the dowel.

2 Push the dowel into the baseboard. Glue a penny onto the inside center of a cup. Glue magets around the outside edge of the cup. Balance the cup on the pushpin. Build an electromagnet by wrapping electrical wire around a nail. Connect one end of the wire to one end of the battery. Wrap the other end of electrical wire around a paperclip. Tape a brass fastener onto the free side of the battery. To charge the electromagnet, connect the paperclip to the brass fastener.

3 Hold the electromagnet near the balancing cup. Turn the magnet on and off. Notice how the electromagnet affects the movement of the cup. Fine Points: Depending on the strength of the battery and the size of the wire, the electromagnet may get hot if left on for a while; it means the battery is dying and may cause small burns. You may also try bunching the coil of wire on top of itself near the head of the nail instead of covering the length of it, to see which works better. Experiment with the strength of the electromagnet by increasing and decreasing the number of wraps around the nail and see if it affects the movement of the cup. By switching the electromagnet on and off at the right moments, you can make the protomotor spin around. Objectives: During this activity students will: 1. Learn to build an electromagnet. 2. Understand that an electric current creates a magnetic field. 3. Understand that the number of turns of wire can affect the strength of an electromagnet. Concepts Involved: Magnetism and electricity are closely related phenomena. Electric currents produce magnetic fields. Different factors affect the strength of electric and magnetic forces. Focus Questions: 1. Does the number of times you wrap the wire around the nail affect the strength of the electromagnet? 2. Does the thickness of the wire affect the strength of the electromagnet? 3. Does the size of the nail effect the strength of the electromagnet? Elaboration: For a long time it was thought that magnetism and electricity were not related. However, in 1820 a Danish scientist named Hans Christian Oersted noticed a magnetic compass move when he turned on a circuit next to it. Later, the work by Michael Faraday and James Clerk Maxwell showed that they are aspects of the same force, now called the electromagnetic force. Electric and magnetic forces can be

4 detected in areas called electric and magnetic fields. Moving electric fields can produce magnetic fields and changing magnetic fields can produce electric fields. This is the basis for understanding electromagnets. In electromagnets, a magnetic field is induced by the flow of an electric current through a coil of wire. As the current flows it creates a magnetic field around the coiled wire, and magnetizes the metal. Electromagnets are useful because you can turn the magnet off; when the flow of electricity stops, the magnetic field disappears. The strength of the magnet is directly related to several things: the number of times the wire is wrapped around the core, the material of the core, the distance from the core to the wire, and the current flowing through the wire. To create a stronger magnetic field, the wire can be more tightly wrapped to decrease the distance from the current to the core. Also, the more loops the current makes around the core the stronger the magnetic field. In the above experiment we used an iron nail for the core. Iron is ferromagnetic, meaning that it can be magnetized in a magnetic field. Cobalt and nickel are also ferromagnetic. There are many examples of electromagnets in your home, such as, doorbells, speakers and electric motors. Links to k- 12 CA Content Standards: Grades k- 8 Standard Set Investigation and Experimentation: Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other strands, students should develop their own questions and perform investigations. Grades k- 12 Mathematical Reasoning: 1.0 Students make decisions about how to approach problems: 1.1 Analyze problems by identifying relationships, distinguishing relevant from irrelevant information, sequencing and prioritizing information, and observing patterns. 1.2 Determine when and how to break a problem into simpler parts. 2.0 Students use strategies, skills, and concepts in finding solutions: 1.1 Use estimation to verify the reasonableness of calculated results Apply strategies and results from simpler problems to more complex problems. 1.3 Use a variety of methods, such as words, numbers, symbols, charts, graphs, tables, diagrams, and models, to explain mathematical reasoning. 2.5 Indicate the relative advantages of exact and approximate solutions to problems and give answers to a specified degree of accuracy. 3.0 Students move beyond a particular problem by generalizing to other situations: 3.1 Evaluate the reasonableness of the solution in the context of the original situation. 3.2 Note the method of deriving the solution and demonstrate a conceptual understanding of the derivation by solving similar problems. 3.3 Develop generalizations of the results obtained and apply them in other circumstances. Grade 4 Standard Set 3. Earth Sciences Electricity and magnetism are related effects that have many useful applications in everyday life. As a basis for understanding this concept:

5 3.a. Students know how to design and build simple series and parallel circuits by using components such as wires, batteries, and bulbs. 3.b. Students know how to build a simple compass and use it to detect magnetic effects, including Earth s magnetic field. 3.c. Students know electric currents produce magnetic fields and know how to build a simple electromagnet. 3.d. Students know the role of electromagnets in the construction of electric motors, electric generators, and simple devices, such as doorbells and earphones. 3.e. Students know electrically charged objects attract or repel each other. 3.f. Students know that magnets have two poles (north and south) and that like poles repel each other while unlike poles attract each other