Download Exemplar Assignment Brief - An Introduction to Electronics at Level 3

Assessment 4
Centre
Canterbury College
Course title: BTEC Extended Diploma in Engineering Level 3
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Capacitors in DC Circuits
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Unit 6 Electrical and Electronic Principles
Scenario
Knowledge of magnetism and electromagnetism is essential in order to underpin futher learning
in electrical subjects. In this assessment you will discover how magnetism is used to produce
and distribute electricity throughout the country and how the same underlying principles are
used in various different types of machinery encountered throughout industry.
Assessment evidence:
Unit
Assessment criteria
The assessment criteria that this assignment relates to:
P7 Describe the characteristics of a magnetic field
P8 Describe the relationship between flux density (B) and field strength (H)
6
P9 Describe the principles and applications of electromagnetic induction
D2 Evaluate the performance of a motor and a generator by reference to
electronic theory
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I certify that the work submitted for this assignment is my own and research sources fully acknowledged.
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Assessment Criteria
P4
P5
P6
M2
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Unit 6 P7
Describe the characteristics of a magnetic field
Draw the magnetic field associated with a permanent bar magnet and use the diagram
to carry out the following tasks.
Give 5 general properties of a magnetic field.
Define flux, flux density and magnetic field strength
Describe the effects of reluctance and hysteresis with respect to magnetic
circuits.
Define the term ferromagnetic and give three examples of a ferromagnetic
material
Describe the process and advantages of magnetic screening
Unit 6 P8
Describe the relationship between flux density (B) and field strength (H)
Plot the B/H curve on a suitable graph for the materials shown on the table from the
given data and determine the relative permeability (µr) of the material for each stage.
Given that µo = 4 x 10-7 H/m find the range of relative permeability for each material.
Use the data plotted on the graph to analyse and explain the relationship between the
two given materials in terms of flux density (B) and magnetizing force (H)
Remember relative permeability µr = B/(H x µo)
Plot the graph that shows relative permeability against the magnetizing force
Describe what happens to a material as the magnetizing force is increased in terms of
flux density and relative permeability
Magnetizing
Force (H) At/m
Mild steel
Flux density (B) Tesla’s
1000
2000
3000
4000
5000
0.7
1.24
1.45
1.55
1.6
Cast Iron
Flux density (B)
Tesla’s
0.3
0.48
0.6
0.67
0.72
Unit 6 P9
Describe the principles and applications of electromagnetic induction
Use the following tasks to describe the principles and applications of electromagnetic
induction.
Define Faraday’ laws in your own words using diagrams where appropriate.
Define Lenz’s law in your own words using diagrams where appropriate.
Draw a diagram of a simple AC generator and use Fleming’s right hand rule to
demonstrate the direction of the current in the rotating conductor when it is
perpendicular to the North Pole.
Explain the principle of operation of a simple transformer with reference to
Faradays law of electromagnetic induction
Explain the principle operation of a 3 phase AC induction motor with reference
to Faradays law of electromagnetic induction
Unit 6 D2
Evaluate the performance of a motor and a generator by reference to electronic theory
Describe the basic operation of a dc machine using diagrams as appropriate. Your
description should include:
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The construction of the machine
Types of field winding
Types of armature winding
A basic description of the action of the commutator
How a dc machine can be used either as a motor or a generator
Calculate the following
a) The no-load terminal voltage of a d.c. generator is 300 volts when working at its
rated speed and nominal flux density. If the speed is reduced by 15% and the flux
per pole is increased by 20% calculate the new value of the no-load terminal
voltage.
b) d.c. motot develops a torque of 500 Nm when carrying an armature current of
25A. What torque is produced if the flux density is increased by 15 per cent and
the armature current is increased to 35A?