ENGR 121
Section______ Instructor:_____________ Name: ____________________________
Form#: 22
Allowed materials include calculator (without wireless capability), pencil or pen.
Honor Statement: On my honor, I promise that I have not received any outside assistance on this exam (I didn’t look at another
student’s paper, I didn’t view any unauthorized written materials, I didn’t talk or listen to another student, . . .).
___________________________________________signature
4 1 2 1
also fill in CWID, name and course (121) . . . don’t forget to black in bubbles
you must show your work on problems that require calculations to receive credit
Problem 1
(2 points) __________ is a photo-reactive chemical applied to the substrate during RTD fabrication and
spun at a high RPM to even out the layer.
a.
b.
c.
d.
Aluminum
UV light
Photoresist
Photomask
e. Development
f. Etchant
g. Bake
Problem 2
(2 points) Which of the following devices is NOT used to sense temperature?
a. RTD
b. Infrared radiation detector
c. Thermometer
d. Bimetallic thermal expansion detection
e. Thermacogenesis
f. Thermistor
g. Thermocouple
h. Integrated circuit sensor
i. Change of state temperature detection - liquid crystals
Problem 3
(2 points) Which of the following partial list of steps is in the correct order for RTD fabrication?
a.
soft bake, spin the photoresist, etch
b.
develop the photoresist, hard bake, etch
c.
etch, hard bake, develop photoresist
d.
spin the photoresist, remove the photoresist, soft bake
e.
hard bake, develop the photoresist, expose to UV light
f.
soft bake, develop the photoresist, expose to UV light
Problem 4
(2 points) Conservation of energy is also known as the first law of
a. motion
b. physics
c. energy
d. nature
e. robotics
f. equilibrium
g. thermodynamics
h. alchemy
i. witchcraft
Problem 5
(2 points) The two semiconductor doping elements discussed in class are _______ and _______.
They have ___ and ___ valence electrons, respectively.
a. Silicon, Boron, 4, 4
b. Silicon, Phosphorus, 4, 3
c. Calcium, Silicon, 2, 4
d. Phosphorus, Boron, 5, 3
e. Carbon, Phosphorus, 4, 5
f. Calcium, Boron, 2, 3
g. Carbon, Boron, 4, 3
h. Silicon, Aluminum, 4, 3
i. Boron, Aluminum, 3, 3
Problem 6
(3 points) Your fishtank has a salinity of 0.30 wt% NaCl. You are interested in opening the DI solenoid
valve to bring the concentration of the tank closer to the setpoint of 0.11 wt% NaCl. The target
concentration if you have a gain of 0.60 (60%) is closest to …
a. 0.044 wt% NaCl
b. 0.054 wt% NaCl
c. 0.087 wt% NaCl
d. 0.110 wt% NaCl
e. 0.186 wt% NaCl
f. 0.190 wt% NaCl
g. 0.414 wt% NaCl
h. 0. 447 wt% NaCl
i. 0.546 wt% NaCl
Problem 7
(3 points) The temperature of a 5 kg sample of an unknown material increases by 12°C when it absorbs
1,500 J of energy. The specific heat of the material is closest to …
a. 25
𝐽
𝑘𝑔°C
b. 124.58
c. 297.6
d. 625
𝐽
𝑘𝑔°C
𝐽
𝑘𝑔°C
𝐽
𝑘𝑔°C
e. 1,517
f. 3,600
𝐽
𝑘𝑔°C
𝐽
𝑘𝑔°C
g. 90,000
𝐽
𝑘𝑔°C
Problem 8
(3 points) A 12VDC power supply powers a 40Ω resistance heater. Select the smallest power supply below
that will sufficiently power the heater.
a. 12V, 0.1A
b. 12V, 0.2A
c. 12V, 0.3A
d. 12V, 0.4A
e. 12V, 0.5A
f. 12V, 0.6A
g. 12V, 0.7A
h. 12V, 0.8A
Problem 9
(3 points) Suppose RRTD=110Ω. Which Rlower value below is most appropriate so that the voltage
drop across the lower resistor is a little less than 1.1V for the given circuit?
5V
a. 20Ω
b. 30Ω
c. 43Ω
d. 51Ω
e. 62Ω
RRTD
analog input
(measures voltage across Rlower)
f. 75Ω
g. 91Ω
Rlower
Problem 10
(3 points) Consider the 12VDC solenoid valve shown below, which is NOT what we used in the fishtank
project. The power in watts required to actuate the valve is closest to …
a. 1.51W
b. 3.00W
c. 7.52W
d. 12.96W
e. 15.00W
f. 18.79W
g. 25.92W
Problem 11
(5 points) A constant current passes through the probes of a conductivity sensor for 15 seconds. If
9.9(10)17 Cl2 molecules are formed, then the value of this current is closest to . . .
a.
b.
c.
d.
e.
f.
g.
h.
1.65 mA
5.23 mA
13.48 mA
21.15 mA
51.39 mA
75.99 mA
100.23 mA
212.54 mA
Problem 12
(5 points) If 14 oz. of salt are added to 5 gallons of water, then the %weight of salt in this mixture is
closest to . . .
a.
b.
c.
d.
e.
f.
g.
h.
0.05%
0.12%
0.78%
1.23%
1.76%
2.06%
5.29%
9.16%
Problem 13
(5 points) An RTD made of nickel has a resistance of 249Ω. If the nickel pattern is 0.2 micrometers thick,
20.75 cm long, and has a resistivity of 1.2 x 10-7 Ω-m, then the width of the nickel trace is closest to . . .
a.
b.
c.
d.
e.
f.
g.
h.
0.125 mm
0.25 mm
0.5 mm
1.0 mm
2.0 mm
5 mm
10 mm
50 mm
Problem 14
(5 points) You are designing a 100 Ω RTD. You have the general
shape of the pattern worked out and just need to determine
the dimension labeled as “x” on the given diagram. This RTD is
made from a material with a resistivity of 1.2 x 10-4 Ω-mm. The
thickness of this material is 0.2 microns, with a line width of
0.5mm. The required length for “x” is closest to . . .
a. 6.65 mm
b. 8.65 mm
c. 10.65 mm
d. 12.65 mm
e. 14.65 mm
f. 16.65 mm
*diagram not drawn to scale
Problem 15
(5 points) You are selecting a resistor to serve as a heater for the new and improved fishtank that
you are designing. You are upgrading to a 16 VDC power supply and want the water to heat at a
rate of 3o C per minute. The fishtank is 1.5 inches in diameter and the water level is 1.3 inches
deep. The resistance value of the heater needed is closest to . . .
a.
b.
c.
d.
e.
f.
g.
h.
16.3 Ω
18.3 Ω
20.3 Ω
22.3 Ω
24.3 Ω
26.3 Ω
28.3 Ω
32.5 Ω
Problem 16
(5 points) A 20 Ω resistor connected to a 18VDC power supply will be used to heat the water in an aquarium
with a volume of 0.01m3. The time it will take to heat the water from 22oC to 27oC is closest to . . .
a.
b.
c.
d.
e.
f.
8,043 s
10,731 s
12,901 s
15,915 s
18,241 s
25,891 s
Problem 17
(5 points) A 50 Ω resistor is used to heat 100 mL of water. It takes 30 seconds for the temperature
of the water to raise 1 degree Celsius. The power drawn by the heater is closest to . . .
a.
b.
c.
d.
e.
f.
10 Watts
12 Watts
14 Watts
16 Watts
18 Watts
20 Watts
Problem 18
(5 points) You have built a new RTD. This RTD is made from a material with a Resistance
Temperature Coefficient (α) equal to 0.004/oC. You have done some preliminary testing and
found that at 25oC the RTD has a resistance of 110 Ω. You expect the resistance at 75oC to be
closest to . . .
a.
b.
c.
d.
e.
f.
g.
124 Ω
126 Ω
128 Ω
130 Ω
132 Ω
134 Ω
136 Ω
Problem 19
(5 points) Given the information below (note: percentages are % weight in water), the mass of Z
is closest to…
120 g
1% NaCl
a. 0.12 kg
b. 0.20 kg
c. 0.34 kg
X
d. 0.42 kg
Mixer
0.04% NaCl
e. 0.58 kg
Z
f. 0.64 kg
0.22% NaCl
g. 0.76 kg
h. 0.82 kg
Problem 20
(5 points) Your fishtank reservoir initially contains 65.9 g of water with a salinity of 0.08% NaCl by
weight. The salty solenoid valve is then opened adding an unknown amount of 1% NaCl solution.
Unfortunately, the end of your overflow tube is clogged so that no water leaves the reservoir (it
accumulates mass since there is no overflow drainage). Your salinity reading stabilizes at 0.18%. The
mass of 1% NaCl solution that was introduced to the reservoir is closest to…
a.
b.
c.
d.
e.
f.
g.
h.
i.
1g
2g
3g
4g
5g
6g
7g
8g
9g
Problem 21
(5 points) Given the voltage divider circuit below (where RRTD = 219Ω and Rlower = 20Ω), if the
Arduino function analogReference(INTERNAL) is used, the analog input reading would be
closest to…
a.
b.
c.
d.
e.
f.
g.
108
274
389
456
530
604
711
5V
RRTD
analog input
Rlower
Problem 22
(5 points) A local sawmill preparing the 2in-by-4in piece of lumber for your fishtank project dries
its freshly cut lumber in a kiln and stores it before shipping. The freshly cut lumber has 50% by
weight water content. The heating process in the kiln results in wood with 35% by weight water
content. Subsequent air-drying during storage results in the moisture content dropping to 24%
by weight water. If the sawmill ships an average of 2000 lbs/day of the air-dried lumber, the
amount of freshly cut lumber delivered to the sawmill is closest to…
a.
b.
c.
d.
e.
f.
g.
2660 lbs/day
2830 lbs/day
3040 lbs/day
3290 lbs/day
3470 lbs/day
3620 lbs/day
3810 lbs/day
Fresh-cut
delivery
Kiln
drying
Air
drying
Ships
2000 lbs/day
Problem 23
(5 points) Nine grams of cream (Cp = 3770 J/kg°C) at 4°C is added to 420
grams of coffee (Cp = 4180 J/kg°C) at 96°C. Assuming no heat loss out of
the cup, the equilibrium temperature of the mixture is closest to:
a.
b.
c.
d.
e.
f.
g.
h.
i.
86.5°C
87.6°C
88.7°C
89.8°C
91.0°C
92.1°C
93.2°C
94.3°C
95.4°C
Problem 24
(5 points) You filled a large water bottle with 1.75 liters of deionized water. The amount of salt in
grams that should be added to make a 0.5% by weight salt water solution is closest to…
a.
b.
c.
d.
e.
f.
g.
6.1 g
8.8 g
11.2 g
14.6 g
18.3 g
22.5 g
26.6 g
Problem 25
(5 points) Dr. Harbour is trying a new method of making his famous alligator soup. He has an immersible
110V, 6.7A resistive heater that he places into in an insulated pot containing 4kg of salty water (C p = 3983
J/kg°C). He heats the salty water to a temperature of 62°C and then adds 2kg of alligator meat (Cp = 3120
J/kg°C) that has an initial temperature of 10°C. Three minutes later, the salty water and the alligator meat
have equalized in temperature. This temperature is closest to: (Notes: The heater heats during the entire
process. Assume zero heat loss from the pot, and uniform temperatures inside the pot at the end of the three
minutes.)
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
51.1 °C
53.3 °C
55.5 °C
57.7 °C
59.9 °C
62.2 °C
64.4 °C
66.6 °C
68.8 °C
70.0 °C
1 coulomb = 6.24(10)18 electrons
Avogadro’s Number: 6.022(10)23
Density of water at 4°C (maximum density) = 1 g/mL = 1g/cm3 = 1000 kg/m3 = 8.33 lbs/gal
𝐶𝑝 𝐻2𝑂 = 4180
𝐽
𝑘𝑔 ∙ 𝐶
1L = 0.001m3 = 1.0567quarts = 0.264gal = 61.02in3
1 pound = 16 ounces = 453.592 grams
Conductivity Sensor Reactions:
2𝐶𝑙 −𝑎𝑞
𝐶𝑙2 (𝑔) + 2𝑒 − and
1 gal = 0.1337 ft3 = 3.785 L
1 inch = 25.4 mm
2𝐻20(𝑙) + 2𝑒 −
1 foot = 12 inches
−
𝐻2 (𝑔) + 2𝑂𝐻(𝑎𝑞)
Atomic Weights:
Na = 23.0 g/mol, Cl = 35.5 g/mol, C = 12.0 g/mol, H = 1.0 g/mol, O = 16.0 g/mol
𝑅=
𝜌∙𝐿
𝐴
𝛼=
Volume of Cylinder =
𝑅2 − 𝑅1
𝑅1 𝑇2 − 𝑇1
𝜋 ∙ 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 2
4
∙ ℎ𝑒𝑖𝑔ℎ𝑡
𝑉 ∙ 𝐼 ∙ 𝑡 = 𝜌 ∙ 𝑉𝑜𝑙 ∙ 𝐶𝑝 ∙ ∆𝑇
∆𝐸 = 𝑄 − 𝑊
/*****************************************************************************/
/* A partial listing of commands recognized by the LCD is provided below.
*/
/* See the data sheet for the LCD on the Parallax web site for more details. */
/* Serial.write(8) - move cursor one space left
*/
/* Serial.write(9) - move cursor one space right
*/
/* Serial.write(10) - move cursor down one line
*/
/* Serial.write(12) - clear screen and move cursor to top left
*/
/* Serial.write(13) - carriage return (will wrap if on last line)
*/
/* Serial.write(17) - turn backlight on
*/
/* Serial.write(18) - turn backlight off
*/
/* Serial.write(21) - turn display off
*/
/* Serial.write(22) - turn display on, cursor off, no blink
*/
/* Serial.write(23) - turn display on, cursor off, character blink
*/
/* Serial.write(24) - turn display on, cursor on, no blink (default)
*/
/* Serial.write(25) - turn display on, cursor on, character blink
*/
/* Serial.write(128) moves the cursor to row 0 and position 0
*/
/* row and position commands are shown below for all 80 character positions */
/*
ROW 0:
128=(0,0) 129=(0,1) 130=(0,2) 131=(0,3) 132=(0,4)
*/
/*
133=(0,5) 134=(0,6) 135=(0,7) 136=(0,8) 137=(0,9)
*/
/*
138=(0,10) 139=(0,11) 140=(0,12) 141=(0,13) 142=(0,14)
*/
/*
143=(0,15) 144=(0,16) 145=(0,17) 146=(0,18) 147=(0,19)
*/
/*
ROW 1:
148=(1,0) 149=(1,1) 150=(1,2) 151=(1,3) 152=(1,4)
*/
/*
153=(1,5) 154=(1,6) 155=(1,7) 156=(1,8) 157=(1,9)
*/
/*
158=(1,10) 159=(1,11) 160=(1,12) 161=(1,13) 162=(1,14)
*/
/*
163=(1,15) 164=(1,16) 165=(1,17) 166=(1,18) 167=(1,19)
*/
/*
ROW 2:
168=(2,0) 169=(2,1) 170=(2,2) 171=(2,3) 172=(2,4)
*/
/*
173=(2,5) 174=(2,6) 175=(2,7) 176=(2,8) 177=(2,9)
*/
/*
178=(2,10) 179=(2,11) 180=(2,12) 181=(2,13) 182=(2,14)
*/
/*
183=(2,15) 184=(2,16) 185=(2,17) 186=(2,18) 187=(2,19)
*/
/*
ROW 3:
188=(3,0) 189=(3,1) 190=(3,2) 191=(3,3) 192=(3,4)
*/
/*
193=(3,5) 194=(3,6) 195=(3,7) 196=(3,8) 197=(3,9)
*/
/*
198=(3,10) 199=(3,11) 200=(3,12) 201=(3,13) 202=(3,14)
*/
/*
203=(3,15) 204=(3,16) 205=(3,17) 206=(3,18) 207=(3,19)
*/
/*****************************************************************************/