# Faraday's Law and Lenz's Law

#### bug13

Joined Feb 13, 2012
2,002
Hi

I am a bit confused about these two laws as they look the same for me. I have checked the definition at Wikipedia but it always give me more questions than answers.

so here is how I understand it, say in a single phase transformer.

The changing voltage (AC) produces a changing magnetic field density at primary, and a voltage is induced on the secondary.

Lenz's Law:
The induced voltage produces a current which tries to keep the original current constant, hence the an inductance in the primary coil.

correct me if I am wrong.

#### WTP Pepper

Joined Aug 1, 2012
21
An AC signal in a winding on a primary core consisting of magnetic material causes a corresponding change in magnetic flux around a core. If you uses a secondary winding to extract this energy set up in the core by the primary by winding a few turns around this core, then you extract such energy in the form of volts. The exact voltage depends upon the number of turns wound around the primary (energy into the core) and the secondary (energy extracted from the core). The more turns means you don't necessarily extract more energy, but more volts and less current. Since power =V x I your either get heavier current at low volts with a few turns or higher voltage with less current.

#### bug13

Joined Feb 13, 2012
2,002
so what does the Lenz's law do to a transformer?

#### MrAl

Joined Jun 17, 2014
11,486
Hi

I am a bit confused about these two laws as they look the same for me. I have checked the definition at Wikipedia but it always give me more questions than answers.

so here is how I understand it, say in a single phase transformer.

The changing voltage (AC) produces a changing magnetic field density at primary, and a voltage is induced on the secondary.

Lenz's Law:
The induced voltage produces a current which tries to keep the original current constant, hence the an inductance in the primary coil.

correct me if I am wrong.

Hi,

Lenz's has the sign in it, which your quoted definitions do not show so it makes them look exactly the same, but Lenz's law should show the negative sign which indicates direction.