Short Answer:

Lenz’s Law states that the direction of the induced current in a closed loop is always such that it opposes the change in magnetic flux that caused it. This means that the induced current produces its own magnetic field that works against the original change in the magnetic field. It helps us know the direction of the current formed due to electromagnetic induction.

Lenz’s Law is directly connected to Faraday’s Law. The negative sign in Faraday’s equation (EMF=−dϕdt\text{EMF} = -\frac{d\phi}{dt}EMF=−dtdϕ​) comes from Lenz’s Law. It shows that the induced EMF always acts to resist the change in magnetic flux, maintaining energy conservation.

Detailed Explanation:

Lenz’s Law and relation to Faraday’s Law

Lenz’s Law was formulated by Heinrich Lenz in 1834. It explains the direction of the current that is induced when the magnetic field around a conductor changes. This law is very important in understanding how electromagnetic induction works in real systems like generators, motors, and transformers.

Faraday’s Law tells us how much EMF is induced when magnetic flux changes. But it does not tell us the direction of the induced current. That part is explained by Lenz’s Law, which gives the correct and consistent direction based on the principle of opposition to change and energy conservation.

Statement of Lenz’s Law

“The direction of the induced current is such that it opposes the change in magnetic flux that caused it.”

In simple words, if you try to increase the magnetic flux through a coil, the induced current will try to decrease it, and if you try to decrease the magnetic flux, the induced current will try to increase it.

This is nature’s way of resisting change, similar to how friction opposes motion.

How it relates to Faraday’s Law

Faraday’s Law gives us the magnitude of induced EMF:

EMF=−dϕdt\text{EMF} = -\frac{d\phi}{dt}EMF=−dtdϕ​

Here, the negative sign is due to Lenz’s Law. It shows that the direction of the induced EMF is such that it opposes the change in magnetic flux. So, Lenz’s Law adds a directional sense to Faraday’s Law and completes the description of electromagnetic induction.

This connection also follows the law of conservation of energy. If the induced current did not oppose the change, it would mean energy is being created from nothing, which is impossible. The opposing nature ensures that extra mechanical work is required to create an induced current, and this work converts into electrical energy.

Examples of Lenz’s Law

1. Falling magnet through a coil:
   When a magnet falls through a coil, the changing magnetic field induces a current in the coil. This current creates a magnetic field that opposes the motion of the magnet, slowing it down.
2. Switching off a current in a coil:
   When the current in a coil is switched off, the magnetic field collapses. Lenz’s Law causes a current to be induced that tries to maintain the original magnetic field.
3. Eddy currents in metals:
   When a metal sheet moves through a magnetic field, circular currents called eddy currents are produced. These oppose the motion and create a braking effect.

Applications 

• Braking systems in trains (magnetic brakes)
• Induction cooktops
• Electric generators and transformers
• Metal detectors
• Energy harvesting systems

These devices all use Lenz’s Law to control, reduce, or convert energy using induced currents.

Conclusion:

Lenz’s Law explains the direction of induced current and ensures that it always opposes the change in magnetic flux. This law completes Faraday’s Law by including the negative sign and helps maintain energy conservation in electromagnetic systems. Together, Lenz’s and Faraday’s Laws form the core of electromagnetic induction, which powers many important electrical machines and systems.