Challenge: To design a generator - motor combination that is as efficient as possible
Parameters: The energy input will be a suspended one kilogram mass falling a distance of one meter. The output energy will be the lifting of UP TO one kilogram a distance of UP TO one meter.
Scoring: Your system will be scored on the basis of the efficiency of the energy transformations. I expect the results will be low, so there will be a factor of 100 included just to avoid decimals:
Score = 10000 * mg∆h / 9.8J
9.8 J is the energy available from a one kilogram mass dropping one meter.
Rank will be based on score, with highest score earning highest rank.
Physics: Conductors spinning in the presence of a magnetic field will experience an induced electromotive force. This is how turbines generate electrical energy for us. When a current flows through a conductor in the presence of a magnetic field, there will be a force on that conductor. This is how motors work. These are simply two aspects of the same physics, but converting mechanical energy into electrical, then back into mechanical will not be very efficient.
Extensions: Some motors with permanent magnets can be used as generators just by spinning them. Some motors are designed to use a lot of current at low voltage, low RPM, and high torque. Others are designed to spin at high RPM etc. You can test motors in class to categorize them. Mr. J will show you how. Try to figure out which kinds are best for the project either by theory or by practice!
Help/Hints: Motors/Generators are more efficient at high RPM. You can use gears, ramps, levers, and pulleys to create a mechanical advantage, but remember that friction is the enemy. Rotating objects have rotational kinetic energy, and they require unbalanced forces (torques) in order to start spinning (or to stop).
Quiz Topics: Electromagnetism (Induction and Forces), Simple Circuits.
Online Text: Ch 22, Ch 23