How is kinetic energy transfer to electrical energy in a permanent magnet and coil interaction?

The below scenarios are based on a bar magnet entering a coil.

When a permanent magnet approaches the coil it produces and electrical current in which in turn produce a magnetic field in the coil. I understand that the electrical current (moves close to speed of light) and magnetic field propagate at the speed of light so the effect is instant. But to generate this electrical current does it means that it is not that efficient in transferring that force to the coil?

I'll give you an example.

A permanent magnet (mass is = 1kg) is traveling at 5ms-1 (Kinetic Energy of Permanent Magnet = 12.5joules) towards an unsecured stationary coil (mass of coil is = 10kg, kinetic energy = 0), When the magnet approaches the coil, the coil will generate an electrical current (lets say 5V 1amp = 5watts) to resist the magnet entering the coil (lets say 5N). So because the coil is unsecured the coil will move in the direction of that 5N force. And lets say this occurs for 2seconds. So the permanent magnet mass and lets say this occurs for 2seconds. So the permanent magnet mass of 1kg is pushing the mass of the unsecured coil at 5N for 2seconds.

Thus (Equation Used = E=1/2mv2)

After The Permanent magnet Exiting the coil.

Velocity of the Permanent magnet is = 2.2ms-1

Velocity of the unsecured coil is = 1.4ms-1

The gross energy of both permanent magnet and unsecured coil should still remain at 12.5joules. Because the force is transmitted directly from the permanent magnet to the coil.


But what occurs to the electrical energy produced by the interaction? There should be at least 5watts of power and 10joules of energy being produced in the electrical circuit.

Do i have to deduct the total energy of 12.5joules with this electrical energy that is being produce?? If i do the kinetic energy of both the permanent magnet and coil will be 2.5joules and most of the energy will be turned into electrical energy.

Is my logic wrong??



2 Answers

  • Anonymous
    7 years ago
    Best Answer

    you are very confused between the physics of moving objects and the interaction of electromagnetic fields

    it tok about 200 years from 1600-1800s to understand mechanics

    then t took another 100 years from 1800 to 1900 to understand electro magnetics

    in physics university fist year is mechanics and second year is intro to e-M

    there is no point in using your numbers they do not represent actual situation

    a changing magnetic filed produces a voltage which may allow current. since everything is changing you cannot use DC electric rules

    energy is conserved it takes mechanical energy to produce the electric energy but in a very very complex way

    Source(s): you have lots to learn but you are trying. keep thinking BS physics retired engineer
  • 3 years ago

    definite. The precipitated contemporary will a) make the coil warmer, possibly via no longer very lots, and b) exert a rigidity on the coil because it contains a contemporary interior the sector of the magnet. If the coil is unfastened to go it is going to benefit KE from the magnet. lower back possibly no longer very lots, yet you never understand!

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