Science Forums 2

[Freethinker]

Originally posted by: nemo
Consider the amount of energy generated from an electromagnet compared with the energy you must provide to power the electromagnet. As a crude example, if you were to place a number of electromagnets in a circle, then place a wheel with magnets attached to it inside the circle, would you be able to rotate the wheel simply by providing current to the electromagnets in sequential order?

As pointed out by Unc, this is basically an electric motor. But by your specific description, it is usually refered to as a "linear motor". Back in the day, when turntables ruled the audio world (oh for the good ole days) some companies developed this drive type for turntable. One attached a magnetic strip inside the platter and applied external magnetic force to "pull" this linear strip (attached at the ends to make a continous circle).

I may be completely off base on this, but my rather juvenile powers of deduction are telling me that you might be able to dramatically increase the milage an automobile can achieve by lining your wheelwells and hubs with electromagnets and corresponding magnets. I couldn't give you a joule ratio for the potential delta in efficiency (sorry, not an EE) but it seems pretty straightforward to me.

Another similar application of linear motor design to transportation is the "Maglev". This is a "train" design which includes superconductors to "levitate" the vehicle and a linear motor the length of the entire track which "positions" the train. By activating the magnetic coils in the appropriate order, the vehicle is moved.

"Fundamentals of Maglev"

http://www.calpoly.edu/~cm/studpage/clottich/fund.html


There is also the "rail gun". Which fires a metal object via magnetic pulses

"Railgun Construction"

http://www.railgun.org/


Or the "Coil Gun"

"The aim of this site is to present experimental research information on coilguns and related topics. In this capacity we hope to foster interest in the fields of physics and engineering. All significant developments will be posted.

Our long term objective is to design and construct single and multi-stage coilguns capable of firing projectiles at supersonic speeds.

http://www.coilgun.eclipse.co.uk/index.html


Bottom line, linear magnetic motor design is highly efficient but requires significant infrastructure. e.g. while it would be a highly efficient method of moving a "car", it would require some magnetic infrastructure running the entire length of the "road".