Answer / 7anoter4

In a close circuit [in a loop] the current flowing in the
conductor produces a magnetic flux [F]. F=L*i [L=circuit
inductance, i=instantaneous current intensity].
In a.c. the flux will change from maximum positive to
maximum negative and again to maximum positive-ideal sine
wave form-in a full wave time-and in turn will produce a FEM
[equal to supply voltage-if we neglect the conductor
resistance].
v=L*di/dt -current derivate in time.
If i=Imax*sin(w*t)[ considering i=0 when t=0] w=2*pi()
*f f=frequency[50 or 60 Hz]
Simplifying: d(sin(wt))/dt=w*cos(wt) and d(cos(wt))/dt=-
w*sin(wt).
v=L*w*Imax*cos(w*t) if L*w*Imax=Vm then:
v=Vm*cos(w*t)
Since at time 0 voltage v=Vm but i=0 and i=Im will be
only after 1/4 of a wave , voltage leads the current.
In a condenser -capacitor-an electric field is installed
[if in the circuit is a voltage supplied ] and the plates
will be charged in short time accumulating the current. In
d.c. after the charge is finited no current will flow
further.
In a.c. a steady state current will flow following the
voltage variation.
From the relation :Q=C*v Q=electric charge C=Capacity
V=voltage
By definition i=dQ/dt then i=C*dv/dt
since v=Vm*cos(w*t)
dv/dt=-w*Vm*sin(w*t) i=-C*w*Vm*sin(wt) .
At t=0 i=0 but before this at wt=-pi/2 rad[-90 dgr] i=Im
that means current leads[the voltage].
90drg. lead=360-90=270 dgr. lag., of course. Conventional
we take only up to 180 dgr. for the angle between voltage
and current of the same phase.

what is the difference between ac and dc?which one is more efficient?and what r their advantages

1 Answers  

---

why t/f are rated in kva. is it conserned with p.f.

3 Answers  

---

function of apfc pannel

3 Answers  

---

Why cpaciter opposes sudden changes in voltage?and how?

1 Answers  

---

what is the name of the oil is used in transformer?

5 Answers  

---

what are factors to be consider to design a HT & LT motor?

1 Answers  

---

what is meant by star/delta voltages as 440/220 in a 3 phase induction motor, and why it should be connected on STAR IN 3 PHASE SUPPLY

0 Answers   L&T,

---

How to Select a Transformer Rating ?

3 Answers   Tata Steel Limited, Techno Electric and Engineering, Vedanta,

---

Motor and transformer working with same principle so why motor rotates while transformer not?

7 Answers  

---

What is the impedence of Transformer?

2 Answers  

---

I completed my BE EEE degree 2006 .... which license should i apply .... ?????

0 Answers   Real Estate,

---

what is the tolerance of electrical frequency for India? it's .5% or 1%?

8 Answers   Engro,

---