# Electrical Circuits

Resit Assignment

This assignment fulfils the resit requirements to pass this credit.
It must be submitted by 4 p.m. on 17th August 2016.
The report must be submitted ON PAPER to the EEE Resource Centre,
4th floor, Royal College Building, Room Number R4.01.
It can be handed in personally, or posted. Optional, electronic
submission by email is not permitted.
EEE Resource Centre
Ref. EE108 (19260)
University of Strathclyde
Royal College Building
204 George Street
Glasgow G1 1XW, UK
A receipt will be provided.
Submissions after this date and time, or failure to submit, will result in a
mark of zero being returned to Registry.
IMPORTANT:
 You must complete the standard coursework Cover Sheet and attach
it to the front of your solutions. This is available from the EEE
Resource Centre or from
https://moss.strath.ac.uk/eee/sip/site/course-information/eee-
45/Documents/cover11.pdf
sheets.
 Students are reminded of the requirement that the submission is
subject to University and Departmental regulations with regards to
2 of 9
Q1) The circuit shown in Figure Q1 is used as part of an engine
management system for a modern car. It determines when the engine
temperature exceeds a threshold value. The input signal from the
temperature sensor is entered at point A.
(10 Marks Total for Q1)
+ _
A
Input
signal
B
C
1k
R1 = 3k
Figure Q1
Q1A) If the sensor signal shown in figure Q1A is entered at point A,
sketch the signal observed at points B and C. Indicate the actual
magnitudes of the signals. Demonstrate all the calculations used and
5 Marks
-0.012 V
0 V
Figure Q1A
Q1B) The designer decides to alter the design of the circuit. Resistor
R1 is now changed to be 1kΩ. If the sensor signal shown in figure Q1A
is again entered at point A, sketch the signal observed at points B and
C. Indicate the actual magnitudes of the signals. Demonstrate all the
5 Marks
Q2) Analogue to Digital Conversion:
(10 Marks Total for Q2)
Q2A) Explain the difference between an analogue signal and a digital signal.
2 Marks
3 of 9
Q2B) Explain what binary coded decimal (BCD) is.
2 Marks
Q2C) The circuit in Q1 is a form of analogue to digital conversion. Within the
engine management system, we wish to count the number of times the engine
temperature threshold is breached. Therefore, we wish to attach a Binary
Coded Decimal (BCD) counter to point C. Draw a diagram of the BCD counter
circuit we need to construct, and explain in detail how it operates (from the
basis of the JK Flip-Flops). We need to count up to a maximum of 99
temperature warnings.
6 Marks
Q3) Internal Resistance:
(18 Marks Total for Q3)
A B
25V
10 5
20
20
5
5
25
20
30
30
10
Figure Q3
Q3A) For figure Q3, if we wish to measure IAB and VAB, draw a diagram that
shows how we would connect an ammeter and a voltmeter.
2 Marks
Q3B) Explain the impact of the internal resistance in the ammeter and
voltmeter. Ideally, what values would we like them to be and why?
2 Marks
Q3C) A student was asked to design a new voltage meter. Once completed, it
had an internal resistance of 500. She then used it to measure VAB in the
circuit shown in Figure Q3. What is the measured value of VAB and what is the
correct value of VAB ?
10 Marks
4 of 9
Q3D) Draw the circuit showing clearly how she could adapt her meter
connection, using a device or circuit employing an op-amp as taught in the
lectures, to measure the correct value of VAB.
2 Marks
Q3E) In the circuit shown in Figure Q3 (with the voltage meter connected),
what is the power dissipated in the meter?
2 Marks
Q4) Figure Q4 shows a Wheatstone bridge circuit arrangement, with a
Thermistor (RT) as part of it. We can assume that RT = 3.4kΩ at 20oC.
The manufacturer’s sheet gives the temperature coefficient of the
thermistor as 5% / oC at 20oC.
(4 Marks Total for Q4)
15 V
1.7k  1.7 k 
RT
A B
3.4k 
3k 
Figure Q4
Q4A) What is the output VAB at 20oC?
1 Mark
Q4B) What is the output VAB at 17oC?
2 Marks
Q4C) Why do we use a Wheatstone bridge for measurement circuits?
1 Mark
5 of 9
Q5) For the circuit shown in Figure Q5:
(4 Marks Total for Q5)
8
5V
A B
4A 3
Figure Q5
Q5A) What is the Thevenin equivalent circuit?
2 Marks
Q5B) What is the Norton equivalent circuit?
2 Marks
Q6) With reference to the circuit shown in Figure Q6, determine the
Thevenin equivalent circuit between A and B, and calculate what the
voltage across a 3 resistor connected between A and B would be.
(4 Marks Total for Q6)
A B
20A
0.2 0.15
5A
10A 0.05
Figure Q6
6 of 9
Q7) For the circuit on Figure Q7, DESIGN and DRAW the op-amp circuit
which will give an output of –20V
(10 Marks Total for Q7)
2
4 4 2
2
20V
18
Op-amp
Circuit
–20V
Figure Q7
Q8) In the circuit shown in Figure Q8, determine, using Kirchhoff’s laws,
the magnitudes and signs of the currents I1, I2 and I3. Find also the
magnitude and sign of the potential difference VAD.
(8 Marks Total for Q8)
R1=10
R4
=40
+ R2=20
+
V1=1V V3=3V
A B C
D
I1=? I3=?
I2=?
V2=2V
R3=30 +
Figure Q8
7 of 9
Q9) Figure Q9 shows an ultrasonic non-destructive testing probe for a
metal plate:
(15 Marks Total for Q9)
0 2 4 6 8 10 plate
initial
pulse
Echo
1
Echo
2
Oscilloscope Crack/defect
Coupling gel
Figure Q9
Q9A) Describe what is meant by non-destructive testing? Why are ultrasonic
methods good for this?
2 Marks
Q9B) Explain what causes echo 1 and echo 2 on the oscilloscope?
2 Marks
Q9C) Explain the role of the coupling gel?
2 Marks
Q9D) Explain what is meant by pulse repetition frequency (PRF) in ultrasonic
non-destructive testing. Why is this an important value to calculate?
2 Marks
Q9E) If the metal plate in figure Q9 is made of steel, is 10 cm deep, and has
no defects then what is an appropriate PRF that should be used?
5 Mark
Q9F) If we use the pulse excitation circuit shown in Figure Q9F, what value
should R1 be set to?
2 Marks
8 of 9
+5V
0V
R1
C1 = 1μF
150
33
E B1
B2
2
3
1
Figure Q9F
Q10) For the circuit in Figure Q10:
(5 Marks Total for Q10)
2
4
VS
8
16
32
64
32
64
0.1A
Figure Q10
Q10A) What is VS? Show the working.
5 MARKS
Q11) AC Circuits: Calculate the magnitudes and signs of the current i12
which will flow in a 10F capacitor under the following conditions:
(6 Marks Total for Q11)
Q11 A) v12=+50V and decreasing in magnitude at a rate of 104 V/s;
2 MARKS
Q11 B) v12 is constant at a value of 38V;
2 MARKS
Q11 C) v12=-500V and its magnitude is increasing at a rate of 600 V/s;
2 MARKS
Q12) AC Circuits: An ac power source has a peak output voltage of
340V:
(6 Marks Total for Q12)
Q12A) Calculate the power dissipated in a 100 resistor connected to the
source.
2 MARKS
9 of 9
Q12B) What is the rms current flowing through the resistor?
2 MARKS
Q12C) What is the peak value of the current?
2 MARKS
END OF PAPER

READ ALSO :   copy an entire directory structure