The document summarizes key concepts about electricity and electrical circuits. It discusses: 1. Direct current (DC) and alternating current (AC), defining their characteristics. 2. Transformers, explaining how they work to change voltage and current levels in circuits using electromagnetic induction. 3. Electrical power calculations, defining formulas for power, voltage, current and resistance. 4. Characteristics of alternating current, including definitions of peak, root mean square and average values of voltage, current and power. The document provides concise explanations of important electrical concepts with relevant formulas and examples.

1. SchoolDD.com
17
N S
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2. 17
17.1
F 16 F F F F F
I
I
B B I
I
F (Michael Faraday) F F F F F F
F F F
F F F
17.1.1 F F F
I
e Q
I I
P
F F F F F F
F F F F
F F F F F
P Q( ) F F Q P
Q P F F F P Q F F
F F F F F
F
F F www.schoolDD.com 1

3. 17.1.2 F F F
F F F F
F F 2
1
I
N
N
B2 > B1
. F F F F F = 2- 1
I
I
N
N
B2 < B1
. F F F F = 2- 1
I
F F F
F F
F FF F F F F
F F
= 2 - 1
I I
2
1
= 2 - 1
I I
1
2
F F www.schoolDD.com 2

4. F 1
. .
v v
. . . .
N N S S
. . . .
N N S S
17.1.3 F F
y
Q R
N v I
B S
I B
v
P S
x
F PQRS F F
xy F v F B F
F F PQ RS F F PS
QR F F
F
F F www.schoolDD.com 3

5. 17.1.4 F
F 16 F I1 F F
F B F F .
N I1 F B S N v I S
B B 2
F I1 I2 B
v
. F .
F
I2 . F F F I1
F F F
F (Back emf)
F F
1. F v=0 F F I2 = 0
F F F I1- I2 = I1 F F
2. F I2 F F I1 F
F F I = I1- I2 F F (v ) F I2
F F F (Imin)
3. F F I2 F
F F F F F F
F F F F F F
F F F
F 2
F F 12 F F 10 F
F F8 F F F F
F F www.schoolDD.com 4

6. I1
F F I = I1 I2 I2
= - 12 V M
I
8= -
8=
R=
R = 0.25 Ans
17.2
F F
F F F 2
17.2.1
I
N v I S
B 2
I2 B 0 t
v /4 /2 3 /4
F
F
F F F F F
F
F F F
F F
F F F F
F F F
F F F F
F F F F
F I t F F
(Direct Current D.C )
F F www.schoolDD.com 5

7. 17.2.2
I
N v I S
B 2
I2 B 0 t
v /4 /2 3 /4
F
F F F
2 F F
F F F
(Alternating Current A.C. )
F F F F F F
F F F F
I F FV
0 t 0 t
T/2 T 3T/2 2T T/2 T 3T/2 2T
1 1
T 1 F f F
1 F 50 F (
50 Hz) F 50 1 F F 220 F
N S
F F www.schoolDD.com 6

8. F F F F F F
F F FF
17.2.3 3
2 1
N S
3
F F
3 120° F F F F F
F F F
F F 120° F FF F F
F F F F F F F
F
F FV
t 1
t 2
t 3
F F www.schoolDD.com 7

9. F
C B
220 V
2 1
F F
N S F3
3
D A
E F 220 V
3 220 V
( F BDF F F )
3 F 6 F F
F F F F F F F F F
(N) F F 3 F F F F ( L)
F F 3 4 (L 3 +N1
) F F F F
3 F F F F F F F
F F F F F F 3 F
3 3 F F F
F F 3 F F 3 F F FF
F F F F F
F F
F F
F F F F F F F
F F F F
F F F F F
F
F
F F
F F F F
F F www.schoolDD.com 8

10. W = QV
W = ItV (I = Q/t)
W = I2Rt
P=
P=
P = IV
F 3
F F F 110 F F
F F F 100 F 0.20 F 10 F F F
. 220 F . 220,000 F
F P = 110x103 W , R = 0.20 , t = 10 s
. V= 220 V , W = ?
W = I2Rt ---1
F R, t I P = IV
I= = = 500 A
F I 1 , W = (500)2x0.2x10
W = 500,000 J Ans
. V = 220,000 , W = ?
W = I2Rt ---1
F R, t I P = IV
I= = = 0.5 A
F I 1 , W = (0.5)2x0.2x10
W = 0.5 J Ans
- F F F F F F F
F F F F F
3 F F F
F F F F F F
230,000 F F F F F 69,000 F F F
F F F 220 F F F F F F
F
F F www.schoolDD.com 9

11. 17.3 F (Transformer)
F F
I2
F F I1 F
R E2
E1 N1 N2
I1 I2
N1 N2
F F
F F F F F F F
F F
F
F I1 E1 F F
F F ( I1 F ) F F F
F F E2
I2 F F
= =
V1 V2 F F F
F 2
1. F ( N2 > N1 F E2 > E1 ) N1 N2
2. F ( N2 < N1 F E2 < E1 )
N1 N2
F F F
F F F
F F F F
W1 = W2
F F www.schoolDD.com 10

12. P1 = P2 I1V1 = I2V2
P1 = F
P2 =
(Eddy current)
F F
F F F F
F F F F ( P2 < P 1 )
F F
F F F F F F F F F
F F F
F
1. F F F
2. F F F F F - F F
3. = =
4. F N2 > N1 , E2 > E1
F N2 < N1 , E2 < E1
5. P1 = P2
F 4
F 200 50 F
12 F F 0.5 F F F
F F
I1 = 0.5
I2 = ?
E1 = 12
N1 = 200 N2 = 50
=
E 2 = E1
= 12
F F www.schoolDD.com 11

13. E2 = 3 V = V2
P 1 = P2
I1V1 = I2V2
V1 = E1 , V2 = E2
F F 0.5x12 = I2x2
I2 = 2 A Ans
F 5
F 20 100 F F
F 25 F F F F 20 F F F F
25 F F
E1 = 20 R = 25
N1 = 20 N2 = 100
F F 25 F F F F F F
F F (W/ Q) F F
W = QV
V=
E1 = V1 = 20 V
=
E 2 = E1
= 20
E2 = 100 V
V = IR
I2 =
=
I2 = 4 A Ans
F F www.schoolDD.com 12

14. 17.4 F F
i R
V
AC
i F Fv
Im Vm
0 t 0 t
T/2 T 3T/2 2T T/2 T 3T/2 2T
- Im - Vm
F R F AC ( F ) (i)
F F F F (v) F F F
F F
i = Im sin t =
= = =2 f
v = Vm sin t
i v F F t
Im Vm F F
F
F F F F
v = iR
V m = Im R
(p) F
F F www.schoolDD.com 13

15. p = iv
Pm = Im Vm
F i, F Fv, p t
i,v, p
Pm p p , Pm i v
Vm v
Im
i t
0
- Im T/2 T
- Vm
FF F F F 1 F F F
F
i,v
i +
i = F
=0 ( +,-)
0 t
v - T v = F
=0
p p =
Pm p=iv
p
= ½ ImVm
t = ½ Im(Im R) = ½ ( )Vm
0
T
p = Im2 R =
i v
Im Vm
0 t 0 t
- Im - Vm
i2 v2
Im 2 Vm2
i2 = Im2 /2 v2 = Vm2 /2
t t
0 0
T T
F F www.schoolDD.com 14

16. FF
(i2) = ½ Im2 (v2) = ½ Vm2
F F Irms = = F
Vrms = = F F F
F F
p = = ½ ImVm = x = Irms Vrms
F Irms Vrms F F F F F F F F F
F F F F F F I V
, F F
1. i = Im sin t (Im = )
F F v = Vm sin t (Vm = F F )
2. F F F F (V = IR)
v = iR
Vm = ImR
3. F F (P = IV)
p = iv
Pm = Im Vm
p = = = IrmsVrms
4. F
Irms =
Vrms =
F 6
i t i = 2 sin (314t)
.
.
. F Irms
i = Im sin t
F i = 2 sin (314t )
F F www.schoolDD.com 15

17. 2 F
Im = 2 A Ans
= 314
2 f = 314
f= = 50 Hz Ans
Irms = = = A Ans
F 7
40 F , 220 F F F F 220 F
. F
. F
.
. 40 W , 220 V
i
AC
Vrms = 220
. F R
p = 40 W , Vrms = 220 V
P = IV = V
=
R= =
R = 1210 Ans
. F Im
Irms =
Im = Irms
= Irms
=
=
Im = 0.26 A Ans
F F www.schoolDD.com 16

18. . Pm
Pm = ImVm
= Im( Vrms)
= 0.26( x220)
Pm = 80 W Ans
. p
p =
=
p = 40 W Ans
F 8
F F F F F F F F 220 F F F
F F F 10 F F F
F Vrms = 220 V Irms = 10 mA
Vm Vrms =
Vm = Vrms = x220
Vm = 311 V Ans
Im Irms =
Im = Irms = x10
Im = 14 mA Ans
17.5
C i,v
i
iC iC vC F 90°
0 t
V vC
AC
. F i,v t
F C F F F iC
F F F vC F 90°
F F www.schoolDD.com 17

19. i,v
i L
0 vL t
V
iL
AC
F L F F F F vL F
F iL F 90° .
F R,L,C
p
v = Vm sin t i,v p=iv
Pm
R i = Im sin t Im Vm t t
i v p = iv
Pm = ImVm i v
p = Pm/2
p
C i,v p=iv
v = Vm sin t Pm
Im , Vm i
t t
i v i = Im sin ( t + /2) v
p = iv
i v F
Pm = ImVm/2
p =0
p
L v = Vm sin t i,v p=iv
Pm
i v Im , Vm v t t
i = Im sin ( t - /2)
i
p = iv
Pm = ImVm/2 v i F
p =0
F F www.schoolDD.com 18

20. F
F ( XC ) F F
( XL ) F F F F F
F
F R=
XC =
XL =
F XC XL F FF F f F
C F L F
XC = =
XL = L = 2 f L
f= F ( F )
C= ( )
L= ( )
F 9
F F F F F
F 10 F F F F F F F F
F 8.0 , 12.0 6.0 F F F
F
R C L
i
R,C,L F F F 10 mA F Irms = 10
mA
F Vrms = 8 V
F F www.schoolDD.com 19

21. R R= =
R = 800 Ans
Vrms = 12 V
XC XC = =
XC = 1200 Ans
Vrms = 6 V
XL XL = =
XL = 600 Ans
F 10
50 F F F rms 12 F F rms
F
. F F 10 F
. 33
. 20
. R
f = 50 Hz
Vrms = 12 V
V = IR I=
Irms = =
Irms = 1.2 A Ans
.
C = 33 F
f = 50 Hz
Vrms = 12 V
F F www.schoolDD.com 20

22. XC XC = = =
XC = 96.5
Irms = =
Irms = 0.12 A Ans
.
L = 20 mH
f = 50 Hz
Vrms = 12 V
XL XL = L = 2 f L = 2x3.14x50x20x10-3
XL = 6.28
Irms = =
Irms = 1.91 A Ans
17.6 F F
PHILIPS
F
F HR 3312
BLADE SIZE 300 mm (12 )
VOLTAGE 220 V 50 Hz
POWER 45 W
AMPERE 0.25 A
F 0.83 m3/min/W
F F F F F F
F F F rms F (p ) F F
F F
p = IrmsVrmscos
F F F
cos F F F 1 ( = 0°)
F F www.schoolDD.com 21

23. - F i v = 0° --> cos = 1
F i v F 0° --> cos < 1
W t F
p =
W=p t
F
F F F F (W) F F F
F F F (UNIT )
1 F = 1 F
F F F F F ( ) F
F F F
-p F F p F F p
F F
F 11
F F F 485 F F 220 F
. F F F i
. F F F
. F F 0.5 v = 220 W
. F . F F F F F F 3 F F
Fp = 485 W , Vrms = 220 V , t = 0.5x60x60 = 1800 s cos = 1.0
. Irms = ?
p = IrmsVrmscos
Irms = = (cos = 1.0)
Irms = 2.2 A Ans
. R=?
R= =
R = 100 Ans
F F www.schoolDD.com 22

24. . W=?
p =
W = p t = 485x1800
W = 8.73x105 J Ans
. F
F . W = 8.73x105 J (= F )
F F F (=1 F )
W=
W = 0.24 F = 0.24 F
F F 3x0.24 = 0.72 Ans
F 12
i i = 5 sin ( t - 40°) F F v = 15 sin ( t +
20°)
.
. F F F
F i = 5 sin ( t - 40°) v = 15 sin ( t + 20°) FF v i F 20-(-40) = 60° Im =
5 A , Vm = 15 ( i = Im sin t v = Vm sin t)
. cos = ? , = 60°
cos = cos 60°
cos = ½ = 0.5 Ans
.p =?
p = IrmsVrms cos
= x x cos 60 = x x =
p = 18.75 W Ans
F 13
I1 , I2 I3 F F
I2 I1
120 V 40 W
800 W
40 W
I3 y x
F F www.schoolDD.com 23

25. F F F F F F F F
Vrms = 120 V
F F F F F p = IrmsVrms
Irms =
y= = A
x= = A
I1 = = A Ans
I2 = x + I1 = + = 7 A Ans
I3 = y + x + I1 = + + = 7.33 A Ans
17.7 F
N N
L L L
L
F 3 4
N L
F
F
L N
N
L
L
N
N L
F
F F
F F www.schoolDD.com 24

26. F F F F F F
F F F F F F 3
F F( L) ( N) F F L N F F
F F F F F
F
1. F F (cut-out) F F F F
F F F F F F F F
F F F F F F F F F F F F
F F F F
- F F F F
F F F F F F
F F F F F F F F F FF
F
2. F F F F F F
F F F F F
F F F
F F F F F
F 14
F F F F 220 F F F F F F F 600 F
750 F F 100 F F 150 F 40 F3 20 F5 F F
F
F F F
F F Vrms F F 220 V
Irms F F F p = Irms Vrms
Irms =
F F Irms1 =
Irms2 =
F Irms3 =
F Irms4 =
Irms5 =
F F www.schoolDD.com 25

27. Irms6 =
F Irms1 + Irms2 + Irms3 + Irms4 + Irms5 + Irms6 = = 8.27 A
p = 600 + 750 + 100 + 150 + (40x3) + (20x5)
= 1820 W
Vrms = 220 V
Irms = = 8.27 A
F 9A F 10 A F F F 10 A Ans
- F F F 1 Irms F F F F F F
F F F F F F F
F 15
F 100 F5 200 F 5 F F F F F
F 200 F F F F
F F Vrms F F 200 V
Irms F F F p = Irms Vrms
Irms =
Irms = = 0.5 A
Irms = = 1.0 A
F = 0.5x5 + 1.0x5 = 7.5 A
F F 8 A Ans
“
... ”
F F www.schoolDD.com 26