faradays laws lenz law

Faraday’s law, Lenz law

FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION

Faradays law of Electro Magnetic Induction

Basic Requirements1. Magnetic field2. Set of conductors (NOTE: They are just a set

of conductors not a current carrying conductors)

3. Relative space variation or4. Relative time variation

Dynamically Induced emf

Magnetic field – steady/ time invariantSet of conductors – being moved

• This is the emf induced in set of conductors when they are being moved in steady magnetic field.

• The nature of emf induced in DC generator is dynamically induced emf.

Statically Induced emf

Magnetic field –Time variantSet of conductors – stationary• This is the emf induced in set of stationary

conductors placed in time varying magnetic field.

• The nature of emf induced in transformer is statically induced emf.

• Magnitude of statically induced emf can be obtained by Faradays 2nd law

• Direction of statically induced emf can be found by applying Lenz’s law.

Faraday’s law of induction:

[1 loop]

[N loops]

Faraday’s Law of Induction

Lenz’s Law

• The minus sign gives the direction of the induced emf:

• A current produced by an induced emf moves in a direction so that the magnetic field it produces tends to restore the changed field.

Lenz’s LawElectromagnetic Induction

The magnetic is moving away from the coil so the magnetic field is decreasing, thus the current is in a direction to off-set the decrease.

The magnetic is moving toward the coil so the magnetic field is increasing, thus the current is in a direction to off-set the increase.

Electromagnetic InductionFaraday’s Law

Electromagnetic InductionFaraday’s Law