CK-12-Physics - Intermediate

19.5. Summary http://www.ck12.org

19.5 Summary

1. The area vector~Ahas magnitude equal to the area enclosed by a conducting loop (or any other enclosed surface)
   and the direction perpendicular (normal) to the plane of the loop.


2. We use the termfluxto describe the number of magnetic field lines that pass through a particular area in space.


3. The product of the magnitude of the magnetic field vector~B, the magnitude of the area vector, and the cosine of
   the angleθbetween them, is called themagnetic flux,represented with the Greek letter phi(Φ).
   Φ=BAcosθ
   The units of flux areT∗m^2 and are calledwebers.
   1 T∗m^2 = 1 W b


4. Faraday’s Law of Induction applied to a coil ofNturns: The average induced voltage in a coil is equal to the
   product of the number of loopsN(or the number of turns) in the coil and the time rate of change in the magnetic
   flux∆Φ∆t through the coil:

V=−N∆Φ∆t

The negative sign indicates that the induced voltage produces a current whose magnetic field opposes the direction

of the original change in the magnetic flux. This statement is known as Lenz’s Law.

5. Ageneratoris a device that converts mechanical energy into electrical energy.


6. Amotoris a device that converts electrical energy into mechanical energy.


7. Atransformeris a device that transfers electrical energy between two circuits using magnetic induction, usually
   with a change in voltage.
   TransformerEquations
   WhereVpis the voltage in the primary coil,Vsis the voltage in the secondary coil,Ipis the current in the primary
   coil,Isis the current in the secondary coil,Npis the number of turns in the primary coil, andNsis the number of
   turns in the secondary coil.
   Equation A:VVps=NNps
   Equation B:IpVp=IsVs
   Equation C:IIps=NNsp

5.Lightis an electromagnetic wave which propagates through a vacuum with a constant velocity ofc= 3. 00 × 108 ms