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====== Hand-Crank Generator ======


===== What is this lesson? =====

This lesson teaches students more energy generation basics, while also teaching simple gearing concepts.



The lesson in gearing would end with students designing and building their own hand-crank generator to charge a cell phone or other device.

If this lesson interests you, there's lots to do:
  * Write the [[teachers guide|teacher's guide]]
  * Adapt the default [[evaluation form]]
  * Design and upload [[illustrations]]
If you're interested in doing any of that, great! Leave a note on the [[:lesson index#Hand-Crank Generator|lesson index]] that you're taking charge.

Whether or not you're interested in writing a part of this lesson, please leave lots of comments on this page, the teacher's guide, and the evaluation form. Thanks!

===== What this lesson teaches =====

==== Science/Engineering principles ====
electromagnetism, current/voltage, gear ratios, gear or pulley design, 
==== Technical skills ====
CAD design if using gears? construction of gear train / box
==== Design skills ====
calculating necessary gear ratio, design gearbox
==== Other skills ====
teamwork, adapting project to available materials
==== Deliverables ====
students build a hand-crank generator to charge cell phone batteries or other device

===== How this lesson fits into the curriculum =====
PEN lessons that meet the requirement are noted in brackets.
==== Curricular knowledge and skills ====
basic circuits / electromagnetism (dynamo lesson)
==== Extracurricular skills ====
use tools (depending on method of fabricating gearbox), soldering
==== Follow-up lessons ====
incorporate into rechargeable hand-crank LED flashlight?

===== Practical Work =====
==== Demonstrations ====
As in dynamo lesson, teacher can show the voltage produced by a motor spun by hand.  Can then show higher voltage when spun faster (need gears to get high enough voltage to charge a phone battery!)
==== Experiments ====
How high of a voltage can you get while spinning the axle by hand?  How might you increase it more? (Lead up to the explanation of how gearing helps spin the motor faster than you can spin it by hand - demonstration of simple gears)
==== Design/Build Work ====
Students will then design and build their own gearbox as part of a battery charger, with a hand crank geared up to spin a motor, which recharges batteries etc.


===== Logistics/Resources =====
==== Building materials ====
small DC motor (or copper wire and magnets), stiff stock material to build gearbox, material for gears/pulleys (pulleys/belts can be used in absence of gears or proper tools to make them), shafts for mounting gears/pulleys
==== Demonstration materials ====
small DC motor, voltmeter
==== Other materials/equipment ====
whiteboard for gear ratio explanations, and student brainstorming/calculations
==== Classroom logistics ====
Ideal class size 10-20 students. For building work, students split off into teams of 3-4, with one teacher/teaching assistant helping with every group(or two?)

===== Optional Questions =====
**Why should students want to participate in this lesson?**

They will get a useful device, that they can use to convert human energy into electrical energy (super-cool!).  They'll also get a better sense for electromagnetism and gearing, which are useful in a number of other more difficult concepts/projects as well.

**Why should teachers want to teach it?**

Gearing and electromagnetism are both very important concepts to understand, and the project is good practice in taking a theoretical concept and doing calculations to figure out how best to implement it in an actual project. 

**If this lesson (and its prerequisites) were the only PEN lessons someone took, what should they be able to do?**

Explain how to turn rotational motion into electricity, basic gearing and electromagnetism (how a motor works, etc.). Design a gearbox to reach a desired voltage output, build a hand-crank generator.  

**If you had to teach this lesson tomorrow morning, what would you spend tonight working on? (assuming that materials were not an issue)**

Figuring out the best way to have students fabricate gears or pulleys, based on available tools, and figuring out how much of the project to leave to the students' design. 

**If you hadn’t taught this lesson before, what questions would you have for someone who had taught a very similar lesson?**



**If the only materials available were broken radios, TVs, and computers, could you do all the electronics in this lesson? (assuming you had solder, soldering irons, etc.) If not, what would be missing?**



**If the only structural materials available were dish-cloths, cardboard, and plastic bags, could you make the mechanical bits of this lesson? (assume equipment as above) If not, what would be missing?**