Alternating Current
Introduction : -
Alternating Current : -
If the direction of current changes alternatively (periodically) and its magnitude
changes continuously with respect to time, then the current is called alternating
current. It is sinusoidal in nature.
&
To
2
------
+ t
O 3
-
Jo --------------------
The value of AC is
given by :
-
= To sinut
E w =
z =
22u]
where ,
I
= Current at instant
any
.
5/Im= Max "Current
v=
Frequency
w =
Angular frequency
It can be defined as the voltage whose magnitude and direction changes
with time and attains the same magnitude and direction after a definite
time interval. The instantaneous value of alternating emf or voltage is
given by
It is defined as that value of Alternating Current (AC) over a
complete cycle which would generate same amount of heat in a given
resistor that is generated by steady current in the same resistor and
in the same time during a complete cycle. It is also called virtual
value or effective value of AC. It is represented by Irms. Suppose I is
the current which flows in the resistor having resistance R in time T
produces heat H .
In a series L-C-R circuit, when phase φ between current and voltage is
zero, then the circuit is said to be a resonant circuit.
It is the measure of sharpness of the resonance of an L-C-R circuit. It
is defined as the ratio of voltage developed across the inductance or
capacitance at resonance to the impressed voltage, which is the voltage
applied across R.
In AC circuit, both emf and current change continuously with respect to
time. So in it we have to calculate average power in complete cycle (0 → T).
It consists of two coils, primary coil p and secondary coil s,
insulated from each other wounded on soft iron core. Often the
primary coil is the input coil and secondary coil is the output coil.
These soft iron cores are laminated to minimise eddy current loss.
