Download Review 6 unlike poles cause the magnets to attract. like poles cause

Review 6
1.
The two characteristics of all magnets are: they attract
and hold Iron , and, if free to move, they will
assume roughly a south - north position.
2.
Lines of flux always leave the
enter the
pole.
3.
The left-hand rule for conductors states that, when
the
hand is placed on a current-carrying
conductor with the
pointing in the
direction of electron flow, the fingers will point in the
south
left
north pole and
thumb
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Added Questions:
unlike poles cause the magnets to attract.
like poles cause the magnets to repel.
Review 7
sine wave
1.
A
is the graphic representation of AC
voltage or current values over time.
2.
Each phase of three phase AC power is offset by
degrees.
3.
An AC generator produces
cycle(s) per
revolution for each pair of poles.
4.
What is the instantaneous voltage at 240 degrees for a
sine wave with a peak voltage of 150 volts?
120 electrical
one
e= Epeak X sine Ѳ
e= 150 X sine 240
e= 150 X -0.866
e= -129.9
5.
What is the effective voltage for a sine wave with a
peak voltage of 150 volts?
RMS = Epeak X .707
RMS = 150 X .707
RMS = 106.1
________________________
Added Questions:
1. An AC generator produces 2 cycle(s) per
revolution for 4 poles generator
2. The unit for frequency is hertz(Hz)
3. A generator produce 80 cycles in 2 seconds, its frequency is 40 Hz.
4. If peak voltage is 100 volts, how much the peak to peak, 200 volts.
Review 8
1.
The total inductance for this circuit is
10h.
4h
L1
LT = L1 + L2 + L3 + L4
LT = 4h + 2h + 3h + 1h
LT = 10h
2.
The total inductance for this circuit is
2h
3h
L2
L2
5h
1/LT = 1/L1+ 1/L2 + 1/L3
1/LT = 1/5 + 1/10 + 1/10
1/LT = 2/10 + 1/10 + 1/10
1/LT = 4/10
LT = 10/4 = 2.5h
The total capacitance for this circuit is
C1
1/CT = 1/C1+ 1/C2 + 1/C3
1/CT = 1/5 + 1/10 + 1/10
1/CT = 2/10 + 1/10 + 1/10
1/CT = 4/10
CT = 10/4 = 2.5F
The total capacitance for this circuit is
C1
5F
CT = C1 + C2 + C3
CT = 5F + 10F + 10F
CT = 25F
10h
L4
10 F
10 F
C2
C3
25F.
C2
10 F
L3
10h
2.5F .
5F
4.
L3
2.5h.
L1
3.
1h
C3
10 F
________________________
Added Questions:
1. What is the unit of measurement for inductance, henry (h).
2. The force that opposes the change in current is Inductance.
3. List things that affect inductance?




number of turns in the coil
coil diameter
Length of coil
core material.
4. The symbol that indicate inductance is
5. Find the total time for current to rise from zero to maximum
t = 15/5 = 3 second
total time = 3 X 5 = 15 second
6. What is the unit of measurement for capacitance, Farads (F).
7. List things that affect capacitance?
 Area of the plates
 Distance between the plates
 Type of dielectric material used.
8. The symbol that indicate capacitance is
9. Find the total time for current to rise from zero to maximum
t = RC
t = 2 X 10 = 20 seconds
total time = 20 X 5 = 100 seconds
Review 11
1.
If the primary of a transformer has more turns than the
secondary, it is a
transformer.
step down
2.
If the primary of a transformer has fewer turns than the
secondary, it is a
transformer.
step up
3.
The secondary voltage of an iron-core transformer with
240 volts on the primary, 40 amps on the primary, and
20 amps on the secondary is
.
480 volts
Es = Ep X Ip /Is
Es = 240 X 40/ 20
Es = 9600/20 = 480v
4.
A transformer with a 480 volt, 10 amp primary, and a
240 volt, 20 amp secondary will be rated for
4.8 kVA.
kVA = Volts X Amps / 1000
kVA = 480 X 10/1000 = 4.8 kVA
or
kVA = 240 X 20/1000 = 4.8 kVA
________________________
Added Questions:
Wire size and voltage drop
1. Which of the following wires has the greatest cross-sectional area?
a.
b.
c.
d.
14 AWG
10 AWG
30 AWG
20 AWG
2. Which of the following wires has the smallest cross-sectional area?
a.
b.
c.
d.
14 AWG
10 AWG
30 AWG
20 AWG
3. A wire that has a diameter of 0.085 inches. How much its circular mils?
1 mil = 1/1000 inch
0.085 inches = 85/1000
85/1000 inches = 85 mils
Circular mils = 85 X 85 = 7225
4. If a current of 20 amps flows through 90 feet Copper wires that has a
diameter of 0.085 inches. How much voltage the wire will drop?
The equations that we use is
Resistance ( R ) = K x L
CM
Voltage Drop ( V ) = I x R
---------------------------------------------------( K ) for copper is = 10.4
( L ) wire length = 90x2 = 180 feet
( CM ) circular mils = 85 x 85 = 7225
( I ) current = 20 Amps
----------------------------------------------------Then
R = 10.4 x 180 = 0.259 ohms
7225
V = I x R = 20 x 0.259 = 5.18 volts
5. From the table, what is the circular mils for the following :
e.
a.
b.
c.
14 AWG
10 AWG
30 AWG
20 AWG
14 AWG = 4107
10 AWG = 10380
30 AWG = 100.5
20 AWG = 1022
‫صمم دائرة كهربائية تحتوي التالي‪:‬‬
‫‪ 3 .1‬لمبات (أحمر‪ ،‬اخضر‪ ،‬ازرق)‪.‬‬
‫‪ .2‬يتم فتح وإغالق اللمبات عن طريق مفتاح واحد‪.‬‬
‫‪ .3‬تكون اللمبة الحمراء مختلفة من حيث التشغيل عن بقية اللمبات‪ ،‬بحيث‬
‫إذا كانتا اللمبتين الخضراء والزرقاء مقفلتين‪ ،‬تكون اللمبة الحمراء‬
‫ضاوية‪ ،‬و العكس صحيح‪.‬‬
‫‪ .4‬يتم التحكم بالمفتاح اتوماتيكيا عن طريق ارتفاع وانخفاض درجة‬
‫الحرارة‪.‬‬
‫‪ .5‬يجب أن تكون هناك فترة زمنية (‪ 5‬ثواني) قبل أن تضيء اللمبتين‬
‫الخضراء والزرقاء‪.‬‬
‫صمم الدائرة وذلك برسمها على طريقة المخطط السلمي‪ ،‬و من ثم حدد‬
‫القطع المطلوبة لتنفيذ المخطط‪ ،‬ثم قم بتوصيل القطع باستخدام طريقة‬
‫الترقيم‪.‬‬