Hughes Electrical and Electronic Technology 9th Edition by Edward Hughes John Hiley
Keith Brown
legal principle or case, exploring various perspectives or discussing its implications in practice.2.3. Skills Tested in Law ExamsLegal Analysis and Application: Law exams test a
student’s ability to identify relevant legal issues, apply appropriate laws and precedents, and reach conclusions
Solutions to Exercises
Section One: Electrical Principles
Exercises 1
1. F ma
F
a 80 0.4 m/s2
m 200
2. 2 kN
3. F ma
2
Here the acceleration is that of gravity, i.e. 9.81 m/s
F 10 9.81 98.1 N
4. 9.81 m/s, 19.62 m/s, 29.43 m/s
5. F ma
a 1 10
F 3
0.1 m/s2
m 10 10 3
v at
v
t 5 50 s
a 0.1
6. 625 kN
7. The velocity has no effect on the weight, hence
F ma 10 9.81 98.1 N
The acceleration requires extra force, hence
F ma 10 (9.81 3) 128.1 N
2
8. 0.98 m/s downwards
9. (a) F 5 103 300 10 9.81
3
14 715 N 14.7 kN
90 10
3
(b) W Fd 14 715 10
60
221 10 J 221 MJ
6
221 10
6
61.3 kWh
3.6 10
6
90 10
3
(c) P Fu 14 715 14 715 25
60 60
368 000 W 368 kW
(d) W mu 300 10 25
1 2 1 3 2
2 2
93.75 10 J 26 kWh
6
10. 16 370 Nm
Exercises 2
1. 0.000 005 A 5 106 A 5 A
2. 3 MV
, V
3. R 6 10
I 0.6
4. 40 V
legal principle or case, exploring various perspectives or discussing its implications in practice.2.3. Skills Tested in Law ExamsLegal Analysis and Application: Law exams test a
student’s ability to identify relevant legal issues, apply appropriate laws and precedents, and reach conclusions
V 240
5. I 0.25 A
R 960
6. 2.9 k
V 240
7. I 28.2 10 A 28.2 kA
3
R 8.5 103
8. 5.1 mA
9. V IR 22 5 110 V
10. 1 mA, 0.67 mA
V1
11. I 10 0.1 A
R1 100
V2 100
R 1000 1 k
2
I 0.1
12. 1 k
13. V/V
5
4
3
2
1
I/A
0.2 0.4 0.6 0.8 1.0 1.2
14. R/
1000
800
600
I/mA
10 20 30 40 50 60
15. Q It 2.5 8 20 C
16. 8 C
17. V IR 2 40 80 V
18. 212 Nm
Po
20 10 22 727 W VI
3
19. (a) P
i
0.88
, 22 727
I 94.7 A
240
(b) W Pt 22.727 6 136.4 kWh
Cost 136.4 8 1091 p
20. 83.8%, 146 kJ; 67.2
3
21. 1000 cm has a mass of 1 kg, hence, for the pump
10 9.81 40 9810 W
6
(a) Po 1.5 3
10 60 legal principle or case, exploring various perspectives or discussing its implications in practice.2.3. Skills
Tested in Law ExamsLegal Analysis and Application: Law exams test a student’s ability to identify relevant
legal issues, apply appropriate laws and precedents, and reach conclusions
, For motor, P Pump output 9810
Pump input
p
o
0.9
10 900 W
10 900 10 900
and P 12 824 W 12.82 kW
i
0.85
12 824
(b) P VI I 26.7 A
480
(c) W Pt 12.82 8 102.6 kWh
22. 59.5 , 0.65 p
23. Energy to raise 1 kg of aluminium from 12 °C to 660 °C
950 (660 12) 615 600 J
Latent heat for 1 kg
450 000 J
Heat energy for 1 kg is 615 600 450 000 1 065 600 J
40 1 065 600
(a) Po 11 840 W = 11.84 kW
3600
P 11.84
P o 13.93 kW
i
0.85
(b) Cost 13.93 8 20 2229 p
legal principle or case, exploring various perspectives or discussing its implications in practice.2.3. Skills Tested in Law ExamsLegal Analysis and Application: Law exams test a
student’s ability to identify relevant legal issues, apply appropriate laws and precedents, and reach conclusions
Exercises 3
1. Across 2 resistor, V2 IR2 2 2 4 V
Across 3 resistor, V3 IR3 2 3 6 V
Across 5 resistor, V5 IR5 2 5 10 V
Total voltage V V2 V3 V5 4 6 10 20 V
2. 500 , 0.48 A
V 120
3. R 80
I 1.5
R1 R2 R3 30 30 R3
R3 20
4. 60
30
5. VAB 100 30 V
30 70
VBC VLN VAB 100 30 70 V
VAC VLN 100 V
VBN VBC 70 V
6. 35 V, 5 V, 35 V, 50 V, 10 V
9
7. (a) I6 1.5 A
R6 6
9
I 1.0 A
9
9
I15 0.6 A
15
10