Saturday, 15 December 2012

varying emf  by mechanically rotating a loop of wire in an external magnetic field, a sinusoidally varying electromagnetic force could be obtained in the rotating loop of wire.

Ԑ = ωAB sin ωt

or

Ԑ = Ԑmax sin ωt

where

Ԑmax = ωAB 

ω is the angular speed of rotating coil, A is the cross-sectional area of the coil, B is the magnetic field that the coil is rotated through.

   the resulting alternating current in the coil was found to be

                i = (Ԑmax /R) sin ωt
   
   ω related to the frequency of the alternating current by
             
             ω = 2∏f


The effective current and voltage in an AC circuit
  • current, i start from 0 increase in one direction until reaches max value i(max)
  • decrease to 0 and increase again in the opposite direction 
  • increase negatively to -i(max)

alternating current i as

i =  imax sin(2∏ft)

effective current ieff is defined as a constant current that generates heat in a resistor R at the same  rate as an alternating current

i =  = 0.707imax



voltage, 

V = imax Rsin(2∏ft),  imax R = Vmax
hence,

V = Vmax (2∏ft)

Veff =





No comments:

Post a Comment