Problem Based Learning In Action

A simple electric generator that should cause the light bulb to turn on when the magnets are spun inside the copper coil. Note that the design process allows for, and usually requires multiple iterations of failure and modification before success is achieved.
Problem Based Learning in Action!
Energy has been a common theme for several teacher teams working at PAST these past two weeks.  The eighth grade team from Starling Middle School plan to explore how energy transformed.  The problem is to transform mechanical (kinetic) energy into electrical energy.  The students will research, design, and build a simple electric generator.  Personally, I have always wanted to do this, so I was very excited to help research examples of electric generators built in classrooms.  


Of course, just watching a video of someone building hand powered generator makes me want to build my own. So Elliot and I headed down to the hardware store after the workday was over and acquired all the items we planned to use.  We are unable to light up a flashlight bulb, yet, but we have ideas for why the generator is not working yet.  We will continue to work through the design process in Atlanta, where we have access to a few additional tools.  Please see the design process below for more details.

Problem: How can we generate electricity to turn on a light bulb?
Brainstorm:  Make a generator using magnets and copper coil.  Power the generator using a windmill, water wheel, steam engine, or human power.
Design a Solution:  Human power is abundant in classrooms, so we’ll use that. The design is based on previous work by Bill Beaty, please see this website for details.  An abbreviated procedure is outlined below.
1. Build a cardboard box open at opposite ends.  The box must be large enough that the magnets can freely rotate with it.  Use tape to hold the box together.
2. Poke a hole through opposite sides of the box and push the iron rod through the holes.
3. Wrap copper wire tightly around the box to create coils on both sides of the iron rod.
4. Connect the copper wire to the leads of the light bulb.  Wrap one end of the copper wire tightly around the leads using pliers.  Pinch the wire together to make the best possible contact between leads and wire.  Wrap each wire/lead combination in electrical tape.
5. Put the four magnets on the iron rod such that the magnets are orthogonal to the rod.
Build Your Solution: See above procedure.
Test/Evaluate Your Solution: The box of the assembled generator was held between the knees while the iron rod was spun as fast as possible.  No light was observed from the bulb, even in a dark room.
Modify Your Solution: The modifications listed below will be performed in Atlanta.

Possible Problem	Potential Solution
Not enough turns of copper wire.  The example from the internet used 200 turns, we only had 118.	Rebuild the generator using a longer strand of wire (not currently available at the hardware store).
Poor electrical contact between copper wire and light bulb leads.	Solder the wires together.
Magnets are not spinning fast enough, they slip off of the rod at high speed rotation.	Make cardboard spacers to hold the magnets parallel to each other. Use hot glue or crazy glue to adhere the magnets securely to the rod.
Not enough voltage or current is generated to power the light bulb.	Connect the generator to a multimeter and see if a measurable voltage or current is produced.

Share Your Solution:  We have already discussed this process with the eighth grade Starling team.  An important lesson in science and engineering is that just because someone else has already succeeded, the product may still be difficult to build (Please see this article on North Korea’s failed rocket launch).  The students should work through the design process, which usually included iterations of failure and modification.  Hopefully we will reproduce a working model to show as a backup should the students not be able to develop their own working generator.