- Thu May 27, 2004 4:31 pm
#4871
Consider a normal generator with copper wires as its coils etc... as the armature is rotated, an emf is induced in it and we have a current flowing through it. As u know, since the coils will have a finite resistance, power is going to be dissipated in the form of heat in the coils. Copper, having a positive coefficient of thermal resistance (its resistance increases as its temperature increases, linearly) so, in a conventional dynamo, as u rotate the coils faster, a larger emf is induced, hence a larger current & hence greater power dissipation. In effect, as the coil is getting hotter, its efficiency is going down.
Now, coming to my idea... (for which u will need to have a little knowledge about thermistors, rather semiconductors). A little theory first: semiconductors have a negative coeff of thermal resistance. This means that the resistance of a semiconductor actually DECREASES as its temperature INCREASES (this happens in an exponental manner). If the coils are made of semiconductor material (problems involving their fabrication shall not be dealt with right now of course) are replaced by their copper counterparts, this is what i expect will happen: the coils will no doubt have an initial resistance. As the coils rotate in the dynamo, an emf is induced which gives raise to a current in the coils, which will no doubt cause power dessipation (P=i^2R) which literally means heat... which, in this case means lowering of resistance of the coils, which will mean a larger current flows thru them, which in turn means greater power dissipation, which again means lower resistance... & so on and on... it would never stop. Please let me know of any loophole that i may have overlooked.
Reward: well, seeing this actually work would be a reward in itself for me. Perhaps if this thing is named after me, it would be a suitable reward for me!
Now, coming to my idea... (for which u will need to have a little knowledge about thermistors, rather semiconductors). A little theory first: semiconductors have a negative coeff of thermal resistance. This means that the resistance of a semiconductor actually DECREASES as its temperature INCREASES (this happens in an exponental manner). If the coils are made of semiconductor material (problems involving their fabrication shall not be dealt with right now of course) are replaced by their copper counterparts, this is what i expect will happen: the coils will no doubt have an initial resistance. As the coils rotate in the dynamo, an emf is induced which gives raise to a current in the coils, which will no doubt cause power dessipation (P=i^2R) which literally means heat... which, in this case means lowering of resistance of the coils, which will mean a larger current flows thru them, which in turn means greater power dissipation, which again means lower resistance... & so on and on... it would never stop. Please let me know of any loophole that i may have overlooked.
Reward: well, seeing this actually work would be a reward in itself for me. Perhaps if this thing is named after me, it would be a suitable reward for me!