Few days back my friend asked me that what will happen if we take the solenoid magnet assembly in space, can we generate infinite electricity with that way.

Let me display the experiment assembly :

One solenoid made with superconducting material (neglect any side effect) and wires. One magnet. And space ( chosen because we want the assembly to be free of outer forces and other disturbing factors) enter image description here

He said that if we give just one push to the magnet to make it near the solenoid so as to increase and hence change the magnetic flux. Then according to Lenz law solenoid will develop similar pole as that of magnet to repel it. Then due to repulsion magnet will move away and that again flux will change as magnet moves away due to repulsion - this would decrease flux and solenoid develops opposite pole according to Lenz rule and so on

This can create indefinite amount of electricity.

I explained the fact by saying that it is the same energy you gave initially circulating as mechanical and magnetic. ( the solenoid will do negative work when magnet moves away)

But a slight modification in this experiment is confusing me. Consider the same assembly but an extra lamp (bulb) included in the circuit. Now the energy first stored will change into light energy (you can choose any such power dissipating item in its place, if necessary) hence every time the current flows, it will lit up the lamp but this will not stop attraction and repulsion occurring (i suppose)

Is conservation of energy law violated?

  • $\begingroup$ Nice work kelvin, $\endgroup$ Oct 8 '17 at 5:25

The lamp will not stop entirely the attraction and repulsion, but it will resist the electrons moving, reducing the magnetic effect.

  • $\begingroup$ Thank you @ Leif, but as you said that "lamp will not stop entirely the attraction and repulsion." But consider the energy point of view : the magnetic energy will convert into light energy (( because electrons are resisted to moving producing heat or light)). But attraction and repulsion won't stop, again "creating" the energy by changing flux (subsequent attraction and repulsion changes flux) $\endgroup$ Oct 3 '17 at 15:17
  • $\begingroup$ I'm a bit confused. Could you re-explain the setup in a manner that makes it clear exactly what happens to the magnet as it moves through the solenoid? Perhaps then I could see what's wrong with it. $\endgroup$ Oct 3 '17 at 21:03
  • $\begingroup$ Assembly :: closed circuit with solenoid and bulb. A magnet in an isolated system (space). We give a slight push to the magnet towards solenoid (mechanical energy) this will induce the cycle of repulsion and attraction as described above, according to Lenz rule. Now consider energy point of view ::: mechanical energy ¬ magnetic energy of solenoid ¬ light or heat energy of bulb (radiated). But this will not stop the attraction repulsion cycle and that in turn will be changing flux and hence ' making ' emf and magnetic energy of the solenoid. Isnot the energy conservation principle violating??? $\endgroup$ Oct 4 '17 at 1:52
  • $\begingroup$ I still think the answer is correct. The attraction and repulsion will steadily diminish until all energy has been turned into light and heat in the bulb. $\endgroup$ Oct 4 '17 at 4:39
  • $\begingroup$ Really? I mean how? $\endgroup$ Oct 4 '17 at 14:23

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