Posted: September 18th, 2017

A.C. CIRCUITS

MODULE TITLE : ENGINEERING SCIENCE
TOPIC TITLE : A.C. CIRCUITS
TUTOR MARKED ASSIGNMENT 4 (v2.1)
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ENS – 4 – TMA (v2.1)
© Teesside University 2011
Student declaration:
I declare that all the work submitted is my own work and that no part of it has been copied from
any other source without full acknowledgement and complies with the University’s guiding
principles as stated in the Regulations Relating To Academic Misconduct*.
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*http://www.tees.ac.uk/docs/index.cfm?folder=Student%20Regulations&name=Academic%20Regulations
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IMPORTANT
Before you start please read the following instructions carefully.
1. This assignment forms part of the formal assessment for this module. If
you fail to reach the required standard for the assignment then you will be
allowed to resubmit but a resubmission will only be eligible for a Pass
grade, not a Merit or Distinction.
You should therefore not submit the assignment until you are reasonably
sure that you have completed it successfully. Seek your tutor’s advice if
unsure.
2. Ensure that you indicate the number of the question you are answering.
3. Make a copy of your answers before submitting the assignment.
4. Complete all details on the front page of this TMA and return it with
the completed assignment including supporting calculations where
appropriate. The preferred submission is via your TUOL(E) Blackboard
account:
https://eat.tees.ac.uk
5. Your tutor’s comments on the assignment will be posted on Blackboard.
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Teesside University Open Learning
(Engineering)
© Teesside University 2011
Assessment Criteria
This assignment will focus on a.c. circuits. The assignment forms Element 4
of the module’s assessment criteria that covers in part Learning Outcomes 2, 3
and 4 as indicated below.
MODULE LEARNING OUTCOMES
Knowledge and Understanding
1. Describe and explain static engineering systems.
2. Describe and explain simple d.c.and a.c.circuits
Cognitive and Intellectual Skills
3. Apply d.c. and a.c.theory to a variety of well defined circuits.
Practical and Professional Skills
Key Transferable Skills
4. Demonstrate numerical and statistical skills applied to engineering problems
relating to electrical and mechanical science.
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Teesside University Open Learning
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PASS
A solution has been
developed to solve problems
but may include some minor
redundancies or errors.
MERIT
Criteria in excess of the pass
grade.
Suitable equations identified
and applied to produce
correct solutions with the
minimum of assistance.
DISTINCTION
Criteria in excess of the
merit grade.
Problems have been solved
independently with the
importance of
interdependence recognised.
1. For the circuit given in FIGURE 1 the power factor is 0.72 lagging and
the power dissipated is 375 W.
FIG. 1
Determine the:
(i) apparent power
(ii) reactive power
(iii) the magnitude of the current flowing in the circuit
(iv) the value of the impedance Z and state whether circuit is inductive or
capacitive.
2. A 50 kW load operates from a 60 Hz 10 kV rms line with a power factor
of 60% lagging. Determine the capacitance that must be placed in
parallel with the load to achieve a 90% lagging power factor.
3. A series RLC circuit is connected to a 5 V supply, the frequency of the
supply is adjusted to give a maximum current of 11.9 mA at 2.5 kHz. The
Q factor is 70. Determine the component values of the circuit.
120 V
Z R = 10 Ω
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Teesside University Open Learning
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© Teesside University 2011
4. A single phase transformer has the following rating: 120 kVA,
2000 V/100 V, 60 Hz with 1000 primary turns.
Determine:
(a) the secondary turns
(b) the rated primary and secondary currents
(c) the maximum flux
(d) given a maximum flux density of 0.25 T, the cross-sectional area of
the core.
5. An a.c. voltage, V, comprises of a fundamental voltage of 100 V rms at a
frequency of 120 Hz, a 3rd harmonic which is 20% of the fundamental, a
5th harmonic which is 10% of the fundamental and at a phase angle of
1.2 radians lagging.
(i) Write down an expression for the voltage waveform.
(ii) Sketch the waveforms of the harmonic components.
(iii) Determine the voltage at 20 ms.
(iv) Given an ideal V = 100 V rms, what is the percentage error at 20 ms?
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Teesside University Open Learning
(Engineering)
© Teesside University 2011
Teesside University Open Learning
(Engineering)
© Teesside University 2011
Question
No.