BTEC Level 3 Nationals in
Engineering:
Unit 1
Your free sample of the student
book: preparation for
assessment
(BTEC National Engineering: Student Book 1 (with ActiveBook),
ISBN: 9781292141008)
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BTEC Level 3 Nationals in Engineering: Unit 1, Study notes of Engineering
This unit is externally assessed using an unseen paper-based examination. Pearson sets and marks the examination. The assessment must be taken under.
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BTEC Level 3 Nationals in
Engineering:
Unit 1
Your free sample of the student
book: preparation for
assessment
(BTEC National Engineering: Student Book 1 (with ActiveBook),
ISBN: 9781292141008)
UNIT 1
68 Engineering Principles
Getting ready for assessment
This section has been written to help you to do your best when you take the external
examination. Read through it carefully and ask your tutor if there is anything you are not sure
about.
About the test
This unit is externally assessed using an unseen paper-based examination. Pearson sets and marks the examination. The assessment must be taken under examination conditions. As the guidelines for assessment can change, you should refer to the official assessment guidance on the Pearson Qualifi cations website for the latest defi nitive guidance. Make sure you are familiar with the command words and know how to apply them within the context of the examination. The table below shows the command words for each Assessment outcome. Assessment outcome Command words AO1 calculate, describe, explain AO2 calculate, fi nd, solve AO3 fi nd, calculate, describe, draw, explain AO4 calculate, draw AO5 calculate, draw, explain Remember that all the questions are compulsory and you should attempt to answer each one.
Organise your time based on the marks available for each question. Set yourself a timetable for working through the test and then stick to it – do not spend ages on a short 1–2 mark question and then fi nd you only have a few minutes for a longer 6–7 mark question. Try answering all the simpler questions fi rst, then come back to the harder questions. This should give you more time for the harder questions.
UNIT 1
70 Engineering Principles
Sample answers
For some of the questions you will be given background information on which the questions
are based.
Look at the sample questions that follow and our tips on how to answer these well.
Answering applied mathematics calculation questions
- Identify the method required to solve the type of problem set.
- Explain each step and show all your workings.
- Express your answer in appropriate units.
- Check your answer.
Worked example
The velocity of a model rocket fired vertically upwards is given by the equation v = 2 t^2 + 5 t – 11. Find, by use of the quadratic formula, the time when the rocket reached its highest point. (2 marks)
Answer At its highest point the velocity of the rocket will have fallen to 0, so 2 t^2 + 5 t – 11 = 0 The quadratic formula takes the form
x = − b ± √
______________^ b^2 − 4 ac 2 a In this problem: a = 2, b = 5, c = −
so t =
−5 ± √^
______________________^5 2 − 4 × 2 ×^ (^ −11) 2 × 2
= ___________−5 ± 10. 63
= 1.41 or −3.
The negative value is not valid in the context of the question, so check the answer by substituting t = 1.41 into v = 2 t^2 + 5 t – 11: v = 3.96… + 7.03… − 11 = 0 (remember to use unrounded values) The highest point will be reached after 1.41 s.
Where calculations are involved, marks are awarded for ‘knowing a method and attempting to apply it’ at each stage. It is essential, therefore, to show your working and make clear which principle or formula is being applied. Further marks are awarded for accuracy, that is, for reaching the correct numerical answer, only if the relevant method marks have already been awarded.
Answering engineering principles calculation questions
- Identify the variables from the information given in the question.
- Write down the formula you need.
- Substitute numbers into the formula.
- Explain each step and show all your workings.
- Express your answer in appropriate units.
- Check your answer.
Worked example
An engineer is testing an inductor with an inductance of 0.5 H and a resistance of 8 Ω. It is connected to a 120 V 50 Hz a.c. supply.
Calculate the current drawn from the power supply. (3 marks)
Answer
The solution will require the calculation of I (^) rms.
The values given in the question are:
L = 0.5 H, R = 8 Ω, V rms = 120 V, f = 50 Hz
The inductive reactance is X L = 2π fL = 2π × 50 × 0.5 = 157.08 Ω.
The total impedance is given by Z = √
X L 2 + R^2 = √
- 08 2 + 8 2 = 157.28 Ω.
So the a.c. current is I rms = ____ V rms Z
= ______^120
= 0.763 A or 763 mA.
Answering engineering principles short-answer questions –
state
- Read the question carefully.
- Make sure that you make the same number of points as there are marks available in the question.
Worked example
State two sources of energy loss that affect the efficiency of electrical transformers. (2 marks)
Answer
Eddy currents. Hysteresis losses.
This answer provides two accurate points and full marks would be awarded. Command words such as ‘give’, ‘state’ or ‘identify’ can be answered in single words or brief statements. There is no need to write in full sentences because the examiner is only testing your ability to recall information.