# What is Lenz's law?

## Question:

What is Lenz's law?

## Lenz Law

Lenz law describes the behavior of an induced current with respect to the changing magnetic field that produces the induced current. It is a qualitative description of the behavior of the current. It is named after Emil Lenz who formulated Lenz law.

Lenz law states that the direction of the induced current in a conductor creates a magnetic field such that the direction of the magnetic field is opposite to that of the magnetic field that induced the current. This means that the induced current flows in the direction such that it opposes the direction of the change that induced it. Lenz law is encapsulated in Faraday's law of induction

{eq}\displaystyle \varepsilon = -\frac{\partial \Phi_B}{\partial t} {/eq}

where {eq}\varepsilon {/eq} is the induced emf and the term {eq}\displaystyle \frac{\partial \Phi_B}{\partial t} {/eq} is the time-varying magnetic flux. The negative sign reflects Lenz law, this means that the direction of the induced emf, hence the induced current, is oriented such that it opposes the direction of the changing magnetic flux.

Lenz law is observed in a simple experiment where you drop a magnet inside a metal tube. When the magnet is dropped inside the tube, it falls slower than when it is drop outside. This is because when the magnet falls it creates a changing magnetic field which creates a current in the metal tube that creates a magnetic field with opposite direction to that of the magnetic field in the falling magnet. The opposing magnetic field interacts with the magnet such that it falls slower because of their opposite direction. 