Introduction to Engineering
Exam 4
SHOW CALCULATIONS AND UNITS FOR ALL ANSWERS
Problem 1a: The voltage source for the circuit shown below is 12 V: (15 Points)
a. If all three resistors were to be replaced with one single equivalent resistor,
what would be its resistance value?
b. What would be the current flow, i, in this circuit?
c. Which of the following resistors, R1, R2, or R3, would have the largest voltage
change across it?
Given:
R1 = 6 
V = 10 Volts
R2 = 8 
R3 = 2 
a. Req  R1  R2  R3  6  8  2  16 
b. i 
V
10

 0.625Volts
Req 16
R3
8
 V   10  5 Volts
Req
16
Problem 1b: Assume for the circuit shown that the R’s are the light bulbs and that you
have been able to measure and determine the following values: (19 points)
c. R3
Source Voltage
V = 120 Volts
Source Current
ix = 15 Amps
 VR3 
i1 = 10 A
i3 = 3 A
Calculate the missing parameters of:
V 120

 12 
i1
10
V 120
 60 
b. R2  
i2
2
a. R1 
c. i2  i x  i1  i3  15  10  3  2 Amps
Calculate the equivalent resistance, Req, for all three resistors combined
 1
1
1 

Req   

 R1 R2 R3 
1
1
1 
1
 
 
 12 60 40 
1
8
R3 
V 120

 40 
i3
3
If R1 (first bulb) is removed or turned off, what would be the new ix?
i x  i2  i3  5 Amps
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Problem 2: While on vacation, you see a giant sequoia (tree) and wonder how high it is.
You have your max flash camera with you and, from your lab experiments, you know the
focal length of this camera is about 30 mm. You pace off the distance from the place you
took the picture to the base of the sequoia and find it to be 120 meters. When you get the
prints back you measure the image of the giant sequoia on the negative and find it to be
20 mm high. Given this information, how tall is the sequoia? (10 points)
Tree
d
f
Image
This is a problem of similar triangles:
Tree Height
d
120
60
 120 



 f  0.02  
  0.040 meters
f Image Height
f
0.02
 60 
Problem 3: In the camera, the flash capacitor can still be dangerous even with the
batteries removed. Why is this? (6 points)
Capacitors are energy storage devices. Thus even with the power source (i.e. the batteries) removed, it is
possible that there is still energy stored in the capacitor that when discharged will pose a possible threat to
safety.
Problem 4: Two common assembly methods are fixed material location and sequential
assembly. Briefly describe each method. Discuss one common problem with the
sequential assembly line method and briefly describe how you would attempt to solve it.
(9points)
Fixed material location is when all of the materials for a product are brought to a single location and the
product is not moved as it is assembled.
Sequential assembly (also known as an assembly line) is when the product being assembled is moved from
one location to the next location and a new component/components are added to the product.
-- One common problem with this method is called a bottleneck. This occurs when one location
is significantly behind the others and the product begins to pile up at that location. A possible
solution is assign additional labor to the location.
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Problem 5: The following saw tooth waveform was measured on an oscilloscope similar
to the ones that you used in lab. What is the voltage at 11 milliseconds? What is the
frequency and period of the waveform? (6 points)
NOTE: The reference voltage (zero voltage) is indicated by the arrow with the
ground symbol in the middle of the display.
@ 11 ms the voltage reading is +5 Volts
To find the frequency we note that the waveform repeats every 8 milliseconds. Thus
the frequency is:
f 
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1

 250 Hertz
T 0.004
3
Problem 6: Using CADKEY create an isometric (3-D) drawing of the object whose
multi-view drawing is shown below. PRINT THE (3-D) DRAWING. DO NOT LEAVE
YOUR SEAT. THE INSTRUCTOR WILL COLLECT THE DRAWING FROM THE
PRINTER. Make sure your name appears on the drawing! Use print preview to see
the drawing you are sending to the printer. (35 Points)
1 grid space = 0.5 inches
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