Peoples Physics Concepts

14.4 Electromagnetic Induction

14.4 Electromagnetic Induction

• Describe the concept of flux and calculate the induced voltage.


• Apply Lenz law to determine the direction of the induced current in a loop of wire.

Students will learn how to determine the flux and how to calculate the induced voltage. In addition, Students will

learn Lenz law and how to use it to determine the direction of the induced current in a loop of wire.

Key Equations

Φ=N~B·~A Electromagnetic Flux

em f=−

∆Φ

∆t

Faraday’s Law of Induction

Guidance

To understand induction, we need to introduce the concept ofelectromagnetic flux. If you have a closed, looped
wire of areaA(measured in m^2 ) andNloops, and you pass a magnetic fieldBthrough, the magnetic fluxΦis given
by the formula below. Again, the relative direction of the loops and the field matter; this relationship is preserved
by creating an ’area vector’: a vector whose magnitude is equal to the area of the loop and whose direction is
perpendicular to the plane of the loop. The directions’ influence can then be conveniently captured through a dot
product:

Φ=N~B·~A Electromagnetic Flux

The units of magnetic flux are T×m^2 , also known asWebers(Wb).