question on transformer

[jerryyu]

On the primary I can produce 120 volts and on the secondary i can create 240 volts. I placed a motor that will used up 120 volts on the secondary wire-which will turn the voltages of the current back to 120 volts, and then I connected that wire back to the primary. Wouldn't that creates perpetual motions?

[insane_alien]

no, that would not create perpetual motion. it would quickly stop due to resistance and the extraction of energy from the system.

[jerryyu]

what do you mean? how are the energy lost?

 

and what is the resistance from that system?

[insane_alien]

well, everything in there will have electrical resistance meaning that the electrical energy will be converted to heat, there will be losses to radio emission because its an AC system(this will be small) and there will be friction in the electric motor. these are all areas where the electrical energy can leave the system but there is no input of energy so the device will slow down and stop very quickly.

[jerryyu]

but as the energy loses and the voltages drop, the transformer will bring the voltages up again right?

 

by the way, does the electrical resistance in the wire also converts the electrical energy to heat?

 

and then the heat will convert to EM waves?

[Mr Skeptic]

If you think you can make a perpetual motion machine, you know there is an aspect of physics you misunderstand.

 

For example, volts have no energy.

[Bob_for_short]

If you connect the primary and the secondary circuits, you will obtain two primary (parallel or anti-parallel) circuits. Both need an external source of power supply to "operate".

 

If there is no an external source, the current in wires will decay due to Ohm resistance, radiative losses, and the heat released in the transformer core.

[jerryyu]

voltage equals I X R

So in a transformer, you increases the amps but also increases the resistances-which with a higher resistances it also decreases the amps. So what is the point of a transformer then?

[Mr Skeptic]

I think that equation only applies to the maximum current. The point of a transformer is that the same energy can be transferred with less losses due to resistance, or with thinner and therefore cheaper cables. This despite the losses at both ends due to the transformers.