NAME: Hossam Nasr
E-MAIL: Hossam.Nasrr@gmail.com
Please complete as many of the questions below as you can. You may use any resource
you wish but you should not ask other people for help. Please attempt all questions but
it is not necessary that you answer all questions. If you can answer part of a question
but not the whole question, please answer the part that you can. We are more interested
in your thought process than the answers to the questions. Please write notes
explaining your logic or making any points you feel relevant. Please note the time you
start working on the exam.
1. Please indicate if the following statements are true or false (simply write TRUE or
FALSE next to the statement):
A. 1 V × 1 W = 1 HP
False: Cause: 1 HP = 764 watt
B. 1 V × 1 A = 1 Joule-sec-1
True: 1 V = 1 J/C, so: 1 V* 1A = 1 J.A / C, Also, V*A= Watt = J/s
C. 1 m3/sec × 1 Pa = 1 W
False: 1 W = 1 m3/S = 1 N.m /S
D. 1 C/s = 1 A
True: the Amp = the charge of one Coulom per second
E. In a parallel circuit, the branch with the highest resistance has the highest current
(Fals)
F. The impedance of a capacitive circuit depends on the frequency
(True)
2. Please select the choice(s) that correctly complete(s) each of the sentences below.
Please note that you may select more than one choice in any question.
I.
An Ampere-hour is a unit of :
a.
b.
c.
d.
e.
II.
A kilowatt-hour is a unit of :
a.
b.
c.
d.
e.
III.
Power watt
Current
Electric Charge
Electric Energy j
There is insufficient information to answer
Power watt
Current
Electric Charge kw.h = j
Electric Energy kw.h = mega j
There is insufficient information to answer
The resistivity of an insulated wire depends on :
a.
b.
c.
d.
e.
Its length
Its cross-section
The material it’s made of
The insulation material around it
All of the above
f.
g.
IV.
The amount of current that can be carried in a given wire is limited by: the resistance
a.
b.
c.
d.
e.
f.
g.
V.
2 hours
0.5 hours
Never
There is insufficient information to answer
A 100 W light bulb is 10% efficient. If it is lit in a room, what will the heat addition rate be
in the room:
a.
b.
c.
d.
VII.
Its length
Its cross-section
The material it’s made of
The insulation material around it
All of the above
None of the above
There is insufficient information to answer
A 2 kW load will drain a 4 kW battery in:
a.
b.
c.
d.
VI.
None of the above
There is insufficient information to answer
90 W
100 W
110 W
There is insufficient information to answer
A 100 Ω load is connected to a battery with an open-circuit voltage of 12 V and internal
resistance of 10 Ω. The voltage across the load is
a.
b.
c.
d.
e.
12 V
12.5 V
10.9 V
9.93 V
There is insufficient information to answer
Please answer the questions below to the best of your ability.
3. 100 identical electric bulbs are connected in series across a supply of 220 volts. One bulb is
burnt out and replaced with a simple wire (short circuit). After the replacement:
i. Will each of the remaining 99 be brighter or dimmer than the original 100? little
brighter
impact is approximately 5% in rising the voltage,
ii. In total, will the remaining 99 be brighter or dimmer than the original 100?
it is brighter since there is less resistance to the total voltage
iii. How much brighter or dimmer will each of the 99 remaining bulbs be compared with
the original 100?
120/100=1.2V/120 = 1%,
so: 101%*99/100=99.99
iv. How much brighter or dimmer will the 99 bulbs be in total, compared with
the total brightness of the 100 bulbs?
100.01%
4. There are two heating coils of the same material and length. One is thinner and the other
is thicker.
i. If these coils are connected in parallel, which one will draw more power?
the thicker
ii. If the coils are connected in series, which one will draw more power?
the same
Figure 1 Diagram for Problem 5
5. For the circuit in the figure shown above:
a) Please write the current i in terms of the parameters shown in the diagram. You may
assume the wires have no resistance.
I=V/{1/R1 + (1/(R2+R3))}
b) Please write the current through R1, R2, and R3.
I1 =V/R1 , I23 = V/(R2+R3)
c)
Is the voltage at point A larger or smaller than at point B? Is the voltage at point C larger
or smaller than at point B?
Vb= Vc+Va
d) What is the voltage at point A in terms of the parameters shown in the figure?
6. A 2 hp pump has an outlet pipe 5 cm in diameter. The pump is used to pump water and is 90%
efficient. The pump is operating at a flow rate of 95 l/s.
Since: Q=Av, A=78.5 cm2, then v = Q / A = 9.5 m/s
a) What is the expected pressure at the outlet of the pump if the inlet pressure is 0 atm?
𝑝0/γ
b) If the pump operates for 2 hours, how much water has it pumped and how much energy
has it consumed?
even the pressure of 1 kg of water is 0.1MPa , and 1 atm=0.1 Mpa
and H=P/ρ, so: =(10000kg/m2)/(1000kg/m3);=10m;
c)
If the pump were100% efficient, after two hours of operation, how much water would it
have pumped and how much energy would it have consumed? State any assumptions you
make.
7. Assume m1=m2
a) What is F?
F = 2m*g
Assume m1>m2, and they are held in place by a brake on the
pulley. What is F in this case?
Since m1>m2, m1 rises up and m2 goes down.
F = (m1+m2)*a = m1*g - m2*g
b) The brake is released. What is the acceleration of m1 and m2 at
the moment of release?
g
c)
What is the acceleration at the steady-state?
a = g* {(m1-m2)/(m1+m2)}
d) What is F in this case?
F = m1.g + m2.g
Please note how long it took you to complete the exam and please list any sources of
information you used in completing it (in a way that allows us to refer to them). Please
note that the time taken and the resources used will not affect the evaluation of the test.
…………………………………………………………………………………………………………………………………....
I started at 1:08 Pm and i finished at 3:49 Pm .
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https://www.calculator.net/area-calculator.html?circleradius=5&circleradiusunit=centimeters&calctype=ci
rcle&x=81&y=19#circle