# Exploring the Reversal of Lenz Law: What Would Happen?

• get_physical
In summary, Lenz Law states that when a magnet is moved towards a coil, the resulting induced current flows in a direction that produces a magnetic field opposing the motion of the magnet. If Lenz Law were to be reversed, the induced current would flow in the same direction as the motion of the magnet, resulting in a violation of the law of conservation of energy. This is due to the fact that the induced voltage and current both depend on the resistance of the coil, and at low resistance values, the induced current would be constant while the voltage would vary, and vice versa for high resistance values. Considering both the external and internal flux, the induction would result in constant current at low resistance values and constant voltage at high resistance values. Ultimately
get_physical
Question about Lenz Law.

When a magnet is moved towards a coil, it produces a current in the coil. The current flows in the coil in the direction which produces an "induced" magnetic field that pushes away the motion of the approaching magnet. Faster the magnet approaches, bigger the current and the larger the induced magnetic field.

Suppose Lenz Law was exactly the opposite: When you move a magnet towards a coil, the induced magnetic field pulls the magnet closer. What do you think would happen?"

You would have the current flowing in the opposite direction from the real Lenz Law scenario. Although, if Lenz law were the opposite of what it is, I believe you would get a runaway feedback process that would eventually give the currents infinite speed, with the energy coming out of nowhere, thus breaking the law of conservation of energy.

Will the induced magnetic field pull in the magnet instead of opposing it?

Minor comment: The magnet induces a voltage in the coil, and the instantaneous current is the instantaneous voltage divided by the coil resistance.

Bob S said:
Minor comment: The magnet induces a voltage in the coil, and the instantaneous current is the instantaneous voltage divided by the coil resistance.

The magnet induces current & voltage in unison. Is it constant voltage, with current determined as V/R? Or is it constant current, with V determined as I*R?

WIth high R values, constant voltage is induced, I = V/R. But with low R values, I is constant, V = I*R. For example, if the loop is 1 ohm, changing it to 2 ohms results in very nearly the same current with twice the voltage.

If the loop is 1.0 megohm, raising it to 2.0 megohm results in the same voltage with half the current. The R value is critical. Refer to the above link for the equations.

The induced voltage and current both depend upon R, as well as L, and frequency. If R >> X (X = L*omega), we get constant voltage variable current. If R << X, we get constant current variable voltage.

It has to be this way re conservation of energy law - CEL. The magnetic field has a limited power. The induced current-voltage product is power. This power cannot exceed the field power. At low R values, Mother Nature exhibits current source behavior. At high R values, she axhibits voltage source behavior. No surprise at all.

Mother Nature is always conserving energy/power. A low resistance dissipates low power when current source driven, high power when driven from a voltage source, and vice-versa for high R values.

Please examine the equations. It's all there. I'll accept correction, but these equations were posted a couple years ago, & nobody has found an error. Best regards.

Claude

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The basic equation is Faraday's Law:
$$\oint E\space d\ell=V = - N \int_{A}^{} n \cdot\frac{dB}{dt} \space dA$$
The moving magnet induces a voltage V in an N-turn coil. The "induced current" is the induced voltage V divided by the circuit resistance (plus inductance term). The minus sign represents negative feedback producing a magnetic field opposing the magnet, i.e., Lenz Law. If the coil were replaced with a superconducting sheet (similar to a shorted zero resistance coil), the magnet would float above the sheet. See

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Bob S said:
The basic equation is Faraday's Law:
$$\oint E\space d\ell=V = - N \int_{A}^{} n \cdot\frac{dB}{dt} \space dA$$
The moving magnet induces a voltage V in an N-turn coil. The "induced current" is the induced voltage V divided by the circuit resistance (plus inductance term). The minus sign represents negative feedback producing a magnetic field opposing the magnet, i.e., Lenz Law. If the coil were replaced with a superconducting sheet (similar to a shorted zero resistance coil), the magnet would float above the sheet. See

You're assuming that phi and B are entirely due to the external flux. The "B" in your equation includes the contribution due to the induced current. This internal flux opposes the external per law of Lenz. Your mistake is a very common one. You must also remember that E in the left side integral does indeed depend upon R & X.

Please examine my equations per attached link. When both internal and external flux are included, the induction results in constant current at low R values, constant voltage at high R values. Your presentation regards the external flux only. The B in your equation consists of intetrnal Bi plus external Be.

Claude

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get_physical said:
Suppose Lenz Law was exactly the opposite: When you move a magnet towards a coil, the induced magnetic field pulls the magnet closer. What do you think would happen?"
Energy conservation would be violated. As far as laws of physics go, that one is pretty solid.

EDIT: Ah, I see that chrisbaird said this already, and the discussion has moved on. So I'll add that I am with Claude on this one, in fact I remember him setting me straight on this soon after I first joined PF. Yes, the flux through the loop includes that produced by the current in the loop itself, and explains why a superconducting loop has zero EMF in the presences of a changing applied magnetic field: R=0 implies EMF=0 which in turn implies that dΦB/dt=0, or that ΦB is a constant. So the current in a superconducting ring is whatever is necessary to counteract changes in flux of any externally applied B-field.

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## 1. What is Lenz Law and why is it important to explore its reversal?

Lenz Law is a fundamental principle in electromagnetism that states that the direction of induced current in a conductor will be such that it opposes the change that caused it. It is important to explore its reversal because it can lead to new discoveries and advancements in technology.

## 2. How is the reversal of Lenz Law achieved in experiments?

The reversal of Lenz Law can be achieved by using a strong magnetic field to induce a current in a conductor in the opposite direction of what would be expected according to Lenz Law. This can be done by using a powerful electromagnet or a permanent magnet.

## 3. What are the potential applications of reversing Lenz Law?

The potential applications of reversing Lenz Law are vast and varied. It could lead to more efficient and powerful electric motors, generators, and transformers. It could also be used in magnetic levitation technology and in the development of new energy storage methods.

## 4. Are there any limitations to the reversal of Lenz Law?

While the reversal of Lenz Law has many potential benefits, it is not a simple or straightforward process. It requires a significant amount of energy and precise control of magnetic fields. Additionally, there may be unintended consequences or negative effects that need to be considered in the development of practical applications.

## 5. What are the current research and developments in exploring the reversal of Lenz Law?

Currently, there is ongoing research and experimentation in exploring the reversal of Lenz Law. Scientists are exploring new methods and materials to achieve the reversal, as well as investigating potential applications and limitations. There is also a focus on understanding the underlying mechanisms and principles involved in the reversal of Lenz Law.

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