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Module Title: Electronics 1
Year : 1
Module Code: BSC 113
Module Leader: Dr. Ahmed Magdy
Sheet: 1 (Solution)
(a) i = dq/dt = 3 mA
(b) i = dq/dt = (16t + 4) A (c) i = dq/dt = (-3e
-t
-2t ) nA
(d) i=dq/dt = 1200 cos 120 t pA
(e) i =dq/dt =
e t t
4 t ( 80 cos 50 1000 sin 50 ) A
(a) (3t 1) C
q(t) i(t)dt q(0)
(b) (t 5t) mC
2
q(t) (2t s)dt q(v)
(c) q(t) 20 cos 10t / 6 q(0) (2sin(10 t / 6) 1) C
3)(a)At t = 1ms, 2
dt
dq (^) i 40 A
(b)At t = 6ms, dt
dq i 0 A
(c)At t = 10ms, 4
dt
dq i – 20 A
25A, 6 t 8
25 A, 0 t 2
dt
dq i
which is sketched below:
- q= it = 85 x
E = pt = ivt = qv = 3672 x1.2 = 4406.4 J
- For 0 < t < 6s, assuming q(0) = 0,
q t idt q tdt t
t t ( ) ( ) .
0 3 0 1 5
0
2
0
At t=6, q(6) = 1.5(6)
2 = 54
For 6 < t < 10s,
q t idt q dt t
t t
6 6
At t=10, q(10) = 180 – 54 = 126
For 10<t<15s,
q t idt q dt t
t t ( ) ( ) ( )
10 12 126 12 246
10 10
At t=15, q(15) = -12x15 + 246 = 66
For 15<t<20s,
q t dt q
t ( ) ( )
0 15 66
15
Thus,
q t
t
t
t
( )
.
,
1 5
18 54
12 246
66
2 C, 0 < t < 6s
C, 6 < t < 10s
C, 10 < t < 15s
C 15 < t < 20s
The plot of the charge is shown below.
916.7mJ
t 8 2 25016 t-4t 2
250 ( 4 t) dt 2
t t 250 4 t- 2
t 3
w v(t)i(t)dt 10 t(25t)dt 10 ( 25 t)dt 10 ( 100 25 t)dt ( 40 10 t)(100-25t)mJ
40 - 10tV 3 t 4
10 V 1 t 3
10tV 0 t 1
, v(t) 100 - 25tmA 2 t 4
25tmA 0 t 2 i(t)
4
3
2 2
4
3
2
3
2
(^22)
1
2
1
0
3
4
3
3
2
2
1
1
0
- p 1 = 30(-10) = -300 W
p 2 = 10(10) = 100 W
p 3 = 20(14) = 280 W
p 4 = 8(-4) = -32 W p 5 = 12(-4) = -48 W
10) Since p = 0
-306 + 612 + 3V 0 + 28 + 282 - 310 = 0
72 + 84 + 3V 0 = 210 or 3V 0 = 54
V 0 = 18 V
- It should be noted that these are only typical answers.
(a) Light bulb 60 W, 100 W
(b) Radio set 4 W
(c) TV set 110 W
(d) Refrigerator 700 W (e) PC 120 W
(f) PC printer 18 W
(g) Microwave oven 1000 W
(h) Blender 350 W
(a) 12.5A 120
v
p i
(b) . kWh1.125kWh 60
1 5 10 45 60 J 1.
3 w pt
(c) Cost = 1.125 10 = 11.25 cents
(a) 80 mA
10h
08 A h i
(b) p = vi = 6 0.08 = 0.48 W
(c) w = pt = 0.48 10 Wh = 0.0048 kWh
39.6cents
Cost 12 cents 3.
2.4 0.9 3.3kWh
hr 60
hr 1.8kW 60
w pt 12 kW
Energy = (52.75 – 5.23)/0.11 = 432 kWh
energy = (5x5 + 4x5 + 3x5 + 8x5 + 4x10)/60 = 2.333 MWhr
P = 10 hp = 7460 W
W = pt = 7460 30 60 J = 13.43 10
6 J
