NAME:______KEY_____
CAMOSUN COLLEGE
Mechanical Engineering
Technology Program
ECET149 – Electricity and Machines
TERM TEST 1
March 2, 2023
2:30pm, TEC-174
Duration:
Permitted:
50 Minutes
Calculator, One Equation Sheet
Mark
/28
Answer each of the following questions completely on the paper provided.
Use appropriate SI units and prefixes where appropriate.
Marks may be awarded generously based on a neat, clear, solution.



Clearly indicate your answers
Include appropriate SI units in all of your answers
Show your work for full marks on worked problems
Multiple choice (Circle the letter beside your selection)
(1 mark each, 12 marks total)
1. What is the voltage V2 in the circuit shown below?
[Hint: What is the current flowing in this circuit?]
a. 0.5V
𝐼=
b. 2.5V
𝑉2 = 𝐼 × 𝑅 = 500𝜇𝐴 × 1𝑘Ω = 0.5V
c. 12.5V
d. 25.0V
=
=
= 500𝜇𝐴
Or directly using voltage divider rule:
𝑉1 = 𝑉𝑡
= (15𝑉 − 10𝑉) ×
= 0.5𝑉
2. The wiper terminal and one of the two outside terminals of a 100 k  potentiometer are
connected together (i.e. rheostat). If the wiper is set at the center position, what resistance is
expected between the two outside terminals (1-3)?
a. 0 
b. 50 k
c. 80 k
d. 100 k
3. One Watt is the same as one Joule per second; one Watt is also equal to one volt multiplied
by one ampere.
a. True
b. False
4. If the voltage dropped across a resistor increases by a factor of 10 (i.e. multiplying by 10),
the power dissipated by the resistor
a. decreases by a factor of 10
b. increases by a factor of 10
c. increases by a factor of 20
d. increases by a factor of 100
If V increases by 10 times and 𝑃 = 𝐼 × 𝑉 =
power increases by 100 times.
then
Note that if V increases across the resistor by 10 times
then I through the resistor also increases by 10 times.
Test 1 ECET 149 W-2023 afternoon Solution.docxMar 1, 2023
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Test 1 ECET 149 Electricity and Machines
5. In double-subscript notation, VAB = +8 V denotes that:
a. point A is 8 V more positive than point B.
b. point B is 8 V more positive than point A.
c. point A is +8 V with respect to ground.
d. point B is +8 V with respect to ground.
𝑉 = 𝑉 − 𝑉 = +8𝑉
So 𝑉 = 𝑉 + 8𝑉
6. If point “X” in a series circuit measures -3V with respect to ground and point “Y” measures
+7V with respect to ground, then voltage VXY is
a. + 4 V
b. - 4 V
𝑉
= 𝑉 − 𝑉 = (−3𝑉) − (7𝑉) = −10𝑉
c. + 10 V
d. - 10 V
7. In the circuit shown on the right, what is the voltage V L?
a.
8V
b. 12 V
c. 16 V
d. 24 V
No current flows through R2 so the voltage we want
is the same as VR3
R1
𝑅3
1𝑘Ω
= 𝑉𝑠
= 24𝑉 ×
= 8𝑉
𝑅1 + 𝑅3 + 𝑅4
3𝑘Ω
R4
𝑉
R2
R3
e. none of the above
8. Kirchhoff's current law (KCL) states that:
a. the sum of the currents around a closed loop is zero.
b. the sum of the currents entering a junction must equal the sum of the currents
leaving the junction.
c. the sum of the positive currents entering a junction must equal zero.
d. the total current entering a given junction is constant, even with changes in
the supply voltage.
Test 1 ECET 149 W-2023 afternoon Solution.docx
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Test 1 ECET 149 Electricity and Machines
9. A 6  resistor and a 9  resistor are connected in parallel across a 10 V battery.
What is the total current drawn from the battery?
a.
b.
c.
d.
Parallel resistors (R1//R2) so
0.36 A
0.40 A
2.78 A
3.33 A
𝑅 =
×
= 3.6Ω and 𝐼 =
=
=
.
= 2.78𝐴
Or
𝐼 =𝐼
+𝐼
=
+
= 1.67𝐴 + 1.11𝐴 = 2.78𝐴
2
7
X
101
5%
10. A resistor is colour coded with Red-Violet-Brown-Gold bands respectively.
What would be its value and tolerance?
a.
270  +/- 5%
b.
27  +/- 5%
c.
2.7 k +/- 5%
d.
0.27  +/- 5%
11. If you need a 12  resistor with +/- 10% tolerance, what color code should you look for?
a.
BRN-RED-BLK-GOLD
1
2
100
X
10%
b.
BRN-RED-BLK-SILV
c.
BRN-RED-GOLD-SILV
d.
RED-BRN-BLK-GOLD
12. What is the resistance between point A and point B, i.e. R AB.
a. 6 k
b. 12 k
c. 24 k
Four equal resistors (R1, R2, R3, R4) are all in parallel with
each other so
d. 60 k
e. 96 k
𝑅 =
Or
𝑅
24𝑘Ω
=
= 6𝑘Ω
𝑛
4
R1
24 k
R2
A
1
𝑅 =
=
= 6𝑘Ω
1
1
1
1
4
+
+
+
24𝑘Ω 24𝑘Ω 24𝑘Ω 24𝑘Ω 24𝑘Ω
24 k
B
1
R4
R3
24 k
Test 1 ECET 149 W-2023 afternoon Solution.docx
24 k
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Test 1 ECET 149 Electricity and Machines
13. Find the maximum and minimum voltages of VXY that can be achieved
in the following circuit.
(4 marks)
[Hint: The wiper (X-terminal) moves from one end to the other end of the potentiometer, R2.]
a.
Minimum VXY =
2.0V
b.
Maximum VXY =
22.0V
When the wiper is moved all the way to the
bottom of the potentiometer:
28.6V
𝑉
= 28.6𝑉
= 2.0𝑉
When the wiper is moved all the way to the top
of the potentiometer:
𝑉
= 28.6𝑉
14. Wheatstone bridge network
= 22.0𝑉
(4 marks total)
a. What voltage must be dropped across resistor R1 in order to balance the bridge
(ie. make voltage VAB equal to zero)?
(2 marks)
b. What value of resistance must R1 be in order to drop that amount of voltage?
(2 marks)
[Hint: What is the voltage potential of point B (VB) with respect to ground?]
a.
VR1 = ___9V ____
b.
R1 = ___20kΩ _
Lots of ways to solve:
Balanced ∴ 𝑉
= 0 → 𝑉 = 𝑉 so 𝑉
=𝑉
= 9𝑉 so 𝑉
= 9𝑉
𝑉
= 36𝑉
𝑉
= 36𝑉 − 𝑉 = 36𝑉 − 𝑉 = 36𝑉 − 36𝑉
=
→ 𝑅 = 60𝑘Ω ×
= 20𝑘Ω
Test 1 ECET 149 W-2023 afternoon Solution.docx
= 36𝑉 − 27𝑉 = 9𝑉
and 𝑉
= 36𝑉
= 9𝑉
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Test 1 ECET 149 Electricity and Machines
15. Thevenin’s theorem question
(8 marks total)
270 Ω
12V
a. Find the Thévenin equivalent values (Vth, Rth) for the above circuit.
Assume the load will be connected between points A and B.
i.
Vth = ___3.41V _
ii.
Rth = ___523Ω _
(4 marks)
C
270 Ω
12V
𝑉 =𝑉
=𝑉
𝑅
= 330Ω +
=𝑅
= 10
= 3.41𝑉
×
= 523.3Ω
b. What load resistance will maximize the power delivered to the load?
(2 marks)
For max power transfer, RLoad = 523Ω
(Or whatever your Rth is in part a.)
c. What maximum power is delivered to the load you chose in (b)?
(2 marks)
𝑃 = 𝐼𝑉 = 𝐼 𝑅 =
Since Rth = RLoad, VAB = Vth/2 = 1.705V
𝑃=
=
( .
)
= 0.00556𝑊 → 𝑃 = 5.56𝑚𝑊
(Or whatever your value is based on
your results from parts a. and b.)
Test 1 ECET 149 W-2023 afternoon Solution.docx
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