(law of conservation of energy ) apply to electricity & magnetism

In summary: According to lenz's law, the same flux that induced current in the solenoid, will induce mechanical force on the cylnder to stop it.According to lenz's law, the same flux that induced current in the solenoid, will induce mechanical force on the cylnder to stop it.
  • #1
bipin
5
0
(law of conservation of energy!) apply to electricity & magnetism...

ok guys... first look at the PICTURE. (now imagine)

suppose i put SUCH CYLINDRICAL magnet in zero-gravity, perfect vaccum. Then say, i rotate the cylindrical magnet about its axis.

a). what should happen?
->well, there is no any other external force acting on the magnet so that it should rotate about its axis for infinite amount of time...

OK, now i introduce a copper coil (or say... any solenoid) inside the rotating cylingrical magnet... (WITHOUT DISRUPTING ITS MOTION OR ANYTHING)

what should happen?
-> mmm... electricity should be induced in the COIL & can be tapped out from its terminals...

my question?
HERE; it seems like IN THIS situation there is no external force acting to disrupt the motion fo the cylindrical magnet... SO will the magnet rotate about its axis for infinite amount of time? IF SO... electricity will be induced in the coil for infinite amount of time...

<theoritically, it seems impossible> IF this is possible... then the electrical energy that can be used for useful workwhich is taped out from 'this mechanism' (after some time) will be far far far more than the THE INITIAL work done used to rotate the magnet about its centre!

hence law of conservation of energy fails!
& output work will be >>> than input work.

EXPLAIN my doubt!

offtrack: wait! don't tell me the rotation will degrate to a stand still due to the opposing force between electrons & the rotating magnet cauz... SAY! the rotating cylindrical magnet can be MADE up of (say) tens of tons of material so that ITS moment of inertia will be >>> than that opposing force. so it can be compared to... (g=G m1xm2/R^2) so if we jump in the Earth the moment of inertia of Earth is >>> than of US so Earth don't fall on us... we fall on earth! like situation...
 

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  • #2
Any energy you get out will come at the expense of the rotational energy that you supplied. Yes, the rotation will eventually stop. Making the magnet tens of tons will just require that much more energy to get it moving.

Sorry... no free energy.
 
  • #3
the idea for making a bigger magnet was just to justify moment of inertia...

Any energy you get out will come at the expense of the rotational energy that you supplied.
<---AGREED!

----
BUT;
Yes, the rotation will eventually stop.
Yap, other wise it will voilate those basic laws... I KNOW THIS!~

BUT WHY? why should the rotation eventually stop? (i need a proper/convincing scientific explanation, please )
 
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  • #4
bipin said:
<---AGREED!

----
BUT; Yap, other wise it will voilate those basic laws... I KNOW THIS!~

BUT WHY? why should the rotation eventually stop? (i need a proper/convincing scientific explanation, please )

Try this in a clearer fashion...

You are in space, no gravity, etc. etc. A bar magnet is floating by at constant velocity and it drifts into a coil of wire. The ends of the coil are connected to a light bulb. What would happen?

Two things:

1. The bar magnet induces a current in the coil. The current then causes light in the bulb. Energy creation? Nope. Because...

2. The INDUCED CURRENT itself has a "resisting effect" onto the bar magnet. When the bar magnet is moving in, the induced magnetic field due to the induce current will be in such a way as to produce a force RESISTING the intruding magnet. This is Lenz's Law. The bar magnet will slow down! The change in KE of the bar magnet will be equal to the energy induced in the coil (assuming perfect energy transfer).

This is an elementary example of a "self-energy" process, where the object that is causing the effect, in turn gets affected by what it causes.

Zz.
 
  • #5


According to lenz's law, the same flux that induced current in the solenoid, will induce mechanical force on the cylnder to stop it.
 
  • #6


praveenkumard said:
According to lenz's law, the same flux that induced current in the solenoid, will induce mechanical force on the cylnder to stop it.

Just so you know, this is a thread from 2005!

Zz.
 

FAQ: (law of conservation of energy ) apply to electricity & magnetism

How does the law of conservation of energy apply to electricity and magnetism?

The law of conservation of energy states that energy cannot be created or destroyed, only converted from one form to another. This applies to electricity and magnetism because these are both forms of energy. In an electrical circuit, the energy from the power source is converted into electrical energy, which is then converted into other forms of energy such as light or heat. In a magnetic field, energy is also conserved as it is transferred between objects or converted into other forms of energy.

Can the law of conservation of energy be violated in regards to electricity and magnetism?

No, the law of conservation of energy is a fundamental law of physics and cannot be violated. In an electrical circuit, the total amount of energy input from the power source must equal the total amount of energy output. Similarly, in a magnetic field, the total amount of energy transferred or converted must be equal to the initial energy. Violating this law would mean creating or destroying energy, which is not possible.

How do electric and magnetic fields interact with each other in regards to the law of conservation of energy?

Electric and magnetic fields are interconnected and can interact with each other. The law of conservation of energy applies to these interactions, meaning that the total amount of energy in the system must remain constant. For example, in an electromagnetic wave, the electric and magnetic fields are constantly changing and interacting with each other, but the total amount of energy remains the same.

Does the law of conservation of energy apply to all types of electricity and magnetism?

Yes, the law of conservation of energy applies to all types of electricity and magnetism, including static electricity, direct current (DC), and alternating current (AC). This law is a fundamental principle of physics and applies to all forms of energy, including electrical and magnetic energy.

Can the law of conservation of energy be used to predict the behavior of electricity and magnetism?

Yes, the law of conservation of energy can be used to predict the behavior of electricity and magnetism. By understanding this law and how it applies to these forms of energy, scientists can make accurate predictions about the interactions and transformations of electric and magnetic energy in systems. This is crucial in fields such as electrical engineering and physics, where precise predictions are necessary for designing and understanding complex systems.

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