Activity 9b Electrical Generator PHYS 010. To demonstrate a basic electric motor using common lab materials

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1 Name: Date: Partners: Part 1. The Generator Effect. Purpose: To demonstrate a basic electric motor using common lab materials Materials: 1. 6 rare earth magnets 2. 1 AA battery 3. Masking tape or scotch tape 4. About 60 cm of stranded or solid wire 5. Two alligator clips CAUTION: Rare - earth magnets are VERY strong. Take them apart by sliding them do not try to pull them apart. If you get your fingers in between the magnets and they try to snap back together, you will get your fingers pinched, and the author can verify that it really, really hurts! The same precautions about magnets apply do not place these near your laptops, USB drives, Ipods, credit/debit cards, etc. Diagram: AA battery magnets Length of stranded or solid wire Alligator clips Procedure: 1. Group the magnets into a single cylindrical pile. 2. Split the pile in half so you have 3 magnets in each group, leaving about 1.5 cm between each group. Tape these 2 groups to the table. This will require some teamwork, as these magnets are strong, and will not hold with just one small piece of tape. Rev /5

2 3. If the battery is not in a holder, tape the battery onto the table, as shown in the diagram. 4. Place the length of wire so it sits between the groups of magnets, as shown in the diagram. The free ends of the wire should sit close to the terminals of the battery. Tape the wire to the table about 2 cm from each end. 5. Connect an alligator clip to each free end of the wire. DO NOT connect the clips to the battery yet. Observations: 1. PREDICT! What do you think will happen to the loop of wire in between the magnet groups when you connect the alligator clips to the battery? Write down a sentence or two to explain your reasoning. 2. OBSERVE! Touch the ends of the wire to the terminals of the battery. What did you observe? Did you observe a difference if you reversed the direction of the battery? Write down your observations. (Note: only complete the circuit for short periods at a time, or this will drain the battery quite quickly.) Rev /5

3 Questions: 1. What role do the magnets play in this basic electric motor? 2. What would happen if you used more magnets in each group? What would happen if you added more batteries, hence increasing the current in the circuit? 3. What would happen if you reversed the direction of the magnets? (Ex: the north pole or face of the magnets faced away from the battery, instead of towards it.) 4. From what you ve observed, the direction of motion of a wire in this electric motor is therefore due to what two things? 5. What is the difference between an electric motor and an electric generator? How could we generate electricity from this apparatus? Part 2. Building a generator: Purpose: To build a simple wind generator, and to see how the electrical current produced varies with wind speed. Materials: 1. DC motor Rev /5

4 2. Two-blade fan 3. Motor holder 4. Base 5. 2 alligator clips 6. DC ammeter (range between 0 and 1 A) Procedure: 1. Take the small DC motor in the motor holder, and mount the holder onto the blue base. 2. Connect one end of each alligator clip lead to one of the motor s outlets 3. Mount the fan blade assembly onto the motor shaft. 4. Attach the free ends of the alligator clips to the DC Ammeter. 5. Place your generator in front of a room fan or hair dryer, give the blades a little push, and watch it go! Testing and Observations Use the table below to record the results of your trials. Make a number of trials with a variety of wind sources blowing on it, your TA, fan or leaf blower, etc. Trial Wind Source Current (Amps) Questions: 1. What did you observe? Were you able to get consistent results from your wind generator? If not, explain why. 2. If wind energy is essentially pollution free, why isn t its use more widespread here? Can you think of some places where it could be used? Rev /5

5 Summary and Suggestions for the Future: a. What were the important concepts of physics/science that you learned from this activity? What else did you learn? b. Can you think of alternative hands-on ways in which these concepts could be demonstrated? c. What changes (if any) would you make to teach these activities in a Grade 7-8 classroom Rev /5