Eternating
current
Electric current
v V
Direct current (DC) Alternating current (AC)
Its direction remains
unchanged ↳ Its direction changes periodically
↳
.
&
Its magnitude can
change.
↳ Its
magnitude can be constant
It is of two types : -
The simplest sinusoidal Ac is
11) Steady DC - constant magnitude I =
I sinnt
magnitude
I
(11) Variable DC -> Variable
Examples : -
I 2 I
I
*
Sinusoidal Cosinusoidal AC
*
AC .
t
- oo
·
To
O ⑧
3
I 4 I
* *
squar AC
Triangular AC
· O
i
T2
·
t
I
5 I
*
*
Steady DC
.
Triangular AC
O ·
t
& · ·
t
T
,Average current :-
Farg =I <t
Average value of sinusoidal Ac for a full cycle : -
larg =
1sinwtdt =wt]
= (coso-CONT] = (1-1] = 0
For a half cycle -
:
Farg = Isinwt =w
= (CosO-Copw] =-
E
(1 + 1]
=
Physical significance of the average value of AC -
:
of
Id 0q Idc *t
Ideot-Facd
=
2 &
S
==Fallay
of
Fac
2 &
·
qa Ide
The value of AC equivalent to that steady
is DC which transfers the
average
same amount of charge through a circuit in the same amount of time.
Root square (RMS) value of AC
:
mean -
Irms =
/Id
, RMs value of It to Sinwt
:
"sindwt
-
sinzwt =
Irms = T
=
JI Sinwt = all-coswt)at
- Yat-se
Fo J'
.
=
= xT =
Irms
= = 0 707
.
I
Io = 12 Irms = 1 414 Erms
.
For since or cosine function , their ums value of is
any
Peak value
Ums I
12
V Vo Sinnot
Sinusoidal AC
=
Voms =
Physical significance of the ums value of AC -
:
IGROAR
ot
Id R
H =
IGROt
2 &
S
In-d = dt(Fahrms
ot
Fac R
, ·
HR ot
=> Id
ot
Therefore ,
the RMs value of an AC is equivalent to that DC which
dissipates the same amount of heat in the same resistance over the
same time interval .
current
Electric current
v V
Direct current (DC) Alternating current (AC)
Its direction remains
unchanged ↳ Its direction changes periodically
↳
.
&
Its magnitude can
change.
↳ Its
magnitude can be constant
It is of two types : -
The simplest sinusoidal Ac is
11) Steady DC - constant magnitude I =
I sinnt
magnitude
I
(11) Variable DC -> Variable
Examples : -
I 2 I
I
*
Sinusoidal Cosinusoidal AC
*
AC .
t
- oo
·
To
O ⑧
3
I 4 I
* *
squar AC
Triangular AC
· O
i
T2
·
t
I
5 I
*
*
Steady DC
.
Triangular AC
O ·
t
& · ·
t
T
,Average current :-
Farg =I <t
Average value of sinusoidal Ac for a full cycle : -
larg =
1sinwtdt =wt]
= (coso-CONT] = (1-1] = 0
For a half cycle -
:
Farg = Isinwt =w
= (CosO-Copw] =-
E
(1 + 1]
=
Physical significance of the average value of AC -
:
of
Id 0q Idc *t
Ideot-Facd
=
2 &
S
==Fallay
of
Fac
2 &
·
qa Ide
The value of AC equivalent to that steady
is DC which transfers the
average
same amount of charge through a circuit in the same amount of time.
Root square (RMS) value of AC
:
mean -
Irms =
/Id
, RMs value of It to Sinwt
:
"sindwt
-
sinzwt =
Irms = T
=
JI Sinwt = all-coswt)at
- Yat-se
Fo J'
.
=
= xT =
Irms
= = 0 707
.
I
Io = 12 Irms = 1 414 Erms
.
For since or cosine function , their ums value of is
any
Peak value
Ums I
12
V Vo Sinnot
Sinusoidal AC
=
Voms =
Physical significance of the ums value of AC -
:
IGROAR
ot
Id R
H =
IGROt
2 &
S
In-d = dt(Fahrms
ot
Fac R
, ·
HR ot
=> Id
ot
Therefore ,
the RMs value of an AC is equivalent to that DC which
dissipates the same amount of heat in the same resistance over the
same time interval .
