What is AC voltage ? | AC Full Form | Phasor Diagram | Principle of Ac Generator

What is AC voltage and its full form? 

The full form of AC is Alternating Current. Whenever current flowing in a circuit varies in magnitude along with the direction periodically, then it is called Alternating current. In simple Alternating current or Voltage is one which passes periodically and completes a cycle. During the flow of alternating current, it flows in positive direction for the half time period and in negative direction for another half period of time.

Production of Alternating Voltage

The principle of Production of Alternating Voltage is based on Electromagnetic Induction. According to Electromagnetic induction if there is a relative motion between a magnetic field and conductor then an EMF is induced in the conductor. When a load is connected across the Conductor, a current starts to flow in the load. Thus induced EMF depends on strength of the magnetic field and the number of conductors.
What is AC Voltage?

Consider rectangular coil of N Numbers of turn rotating with a constant angular velocity of ω rad/second. in a uniform magnetic field B. The axis of rotation of the Rectangular coil is perpendicular to the magnetic field. let A is the area of the plane of the rectangular coil. let at any instant t, angle swept by the rectangular coil is θ = ωt radian. component of the magnetic field B perpendicular to the plane of the rectangular coil will be BCosωt.
hence Total magnetic flux link with the rectangular coil at any instant of time is given as 

ф = N x BCosθ x A = NBACosωt
According to faraday's law of electromagnetic induction, Induce emf in a coil is given as rate of change magnetic flux.

emf E = rate of change of flux ф 
emf E =  - d(ф) /dt
emf E =  - d(NBACosωt) /dt
emf E = NBAωSin(ωt)
let  E0= NBAω = Maximum induced emf then 
E = E0Sin(ωt)

Analysis of AC Circuit

When AC voltage is applied across the terminal of the AC circuit, the Alternating current starts to flow. Behaviour of Alternating current with different types of circuit elements is different. here we will study about behaviour of alternating current with Resistive, Inductive and Capacitive Circuit.

AC Circuit Consisting Resistor Only

Let A resistor of R Ω is connected between the terminal of the AC generator. Le the Voltage across the resistor is given as e = E0Sin(ωt) ----------(1)
Let I is Alternating Current flowing through the circuit. then I is given as 
AC Circuit

I = V/R
I = E0Sin(ωt) /R 
I =(E0/R)Sin(ωt) 
if we put = E0/R = I0
I0 is maximum  current
I = I0Sin(ωt) -------(2)
from equations (1) and (2) it is clear that the waveform of Alternating Voltage and Alternating Current are identical. When Alternating voltage is applied across a resistive load then there is no phase difference between Voltage and current.


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