TMA03

Always indicate any principles or definitions you are using.
Take care to express all final answers to an appropriate number of significant
figures, but also ensure that any intermediate values, or answers carried
forward to another part, have sufficient significant figures to avoid
propagation of rounding errors.
Please do not repeat the question text from this document in your eTMA
submission as this is likely to be registered as possible plagiarism by our
automatic detection system, and may lead to delays in returning your
assignment.
We recommend that you look over Section 3 of the S217 Introduction and
Guide before starting work on this assignment.

This TMA is designed to test your achievement of the following
learning outcomes for this module:
Knowledge and Understanding: KU2
Cognitive Skills: CS1–CS6
Key Skills: KS1, KS2
Practical and/or Professional Skills: PPS1, PPS2
This TMA contributes 5% towards your overall score for S217.

Question 1 – 20 marks
This question is designed to assess your reflection on your learning, your
communication skills and your engagement with interactive Quiz 3, covering
Units 7, 8 and 9. It also assesses your understanding of domestic electric
power (Unit 10) and your application of physical principles in relevant
situations.
(a) To demonstrate your engagement with Quiz 3, paste into your TMA
answers a screenshot of either the summary page showing your
performance on Quiz 3 or the screen that gives your overall score for this
quiz. It does not matter what score you obtained, we are interested in
your engagement with the quiz. Remember also that you may attempt
the quiz questions as often as you wish, and each question has multiple
variants that will be presented to you in turn, each time you try it. [2]
(b) In a few sentences, describe one thing that you learned from answering
the questions in Quiz 3 that improved your understanding of
gravitational or electric forces, fields or potentials. Your answer should
be clearly explained and you should not need to write more than 100
words to answer part (b).
(Even if you scored full marks on the quiz the first time you tried it,
hopefully you learnt something of relevance in completing it. If you feel
that this was not the case, your statement to this effect should be
supported by your screenshot in part
(c) (i) In Unit 10 Section 5.2 Activity 3, you completed Table 10.2,
reviewing your own use of domestic energy. Before attempting this
activity, which of your electrical household devices would you have
expected to use the most energy per day? Now you have completed
the activity, was your initial assessment correct? Will you alter
your use of your electrical household devices as a result of this
calculation? Clearly explain your answer in one or two sentences.
(ii) Assume that each of the electric lights in your home is a light
emitting diode with a power rating of 11 W and is switched on for
an average over the year of 2 hours per day, and that before the
introduction of energy efficient lighting, all the light bulbs were
rated at 60 W (and switched on for the same length of time). How
many joules of energy has the change in lighting method saved per
year?
(d) As explained in Developing your transferable skills and competencies,
during your study of S217 you are likely to be developing important
employability skills, many of which are also UNESCO’s key
sustainability competencies. In Question 1 of each S217 TMA, you have
the opportunity to reflect on your skills development.
(i) To what extent has reflecting on your skills development been
useful so far in your study of S217?
(ii) How do you feel that reflecting on your skills development will be
useful in the rest of your study of S217 and beyond?
Your answers should be clearly explained and you should not need to
write more than about 50 words to answer part d
Question 2 – 18 marks
This question is designed to test your understanding of gravitational forces
and fields (Unit 8).
Consider two point-like objects M1 and M2, with M1 having four times the
mass of M2. They are placed a distance d apart from each other.
(a) Sketch (in 2-dimensions) the gravitational field lines that are present in
the region of space around the two masses. Show the direction of the
field on the field lines.
(b) Explain quantitatively where you should place a test particle such that
it experiences a net gravitational force of zero from the two point-like
objects. Indicate this position on your diagram.
Question 3
This question is designed to test your understanding of electric potential and
potential energy (Unit 9).
(a) Two point charges with q1 = +3.5 × 10−7 C and q2 = −4.5 × 10−7 C are
initially separated by a distance of r = 2.8 × 10−4 m.
(i) How much energy is required to double their separation?
(ii) What is the electric potential at the point midway between the two
charges when their separation is 2r? [14]
(b) A uniform electric field of magnitude 1.0 × 102 N C−1
exists between two parallel conducting plates, one of which is positively charged and the
other of which is negatively charged. The plates are 1.0 × 10−2 m apart.
(i) Calculate the magnitude of the potential difference between the
plates.
(ii) If a proton is moved from the positive plate to the negative plate,
what is the magnitude of the change in its electrostatic potential
energy?
(iii) If this device operates as a capacitor, how is it able to store
electrostatic potential energy? [10]

Question 4 – 20 marks
This question is designed to test your understanding of electrical circuits
(Unit 10).
(a) The circuit shown in Figure 1 can be used to measure the resistance of a
platinum resistance thermometer (PRT). AB is a uniform resistance
wire of length 1.00 m and C is a sliding contact on this wire. A standard
resistor R is included in the circuit. The position of C is adjusted until
the voltmeter V reads zero.

Figure 1 For use in question 4.
(i) By applying Kirchhoff’s laws to loops ADCA and BCDB, deduce
an expression for the resistance of the PRT in terms of l1, l and the
value of the standard resistor. [5]
(ii) The PRT consists of 9.00 m of wire of diameter 8.4 × 10−5 m. The
voltmeter reads 0 V when l1 = 0.702 m and the standard resistor,
R, has a resistance of 68 Ω. Use these values to calculate a value for
the resistivity of platinum at the temperature of operation. Show
that you have checked that the value for the resistivity and its unit
are sensible.
(b) Indicate briefly what factors might affect the precision of the
measurement when using such a simple circuit to measure the resistance
of the PRT.
page 5 of 6
Question 5
This question is designed to test your ability to evaluate sources of
information (Unit 6) and your communication skills, in the context of the
topic of gravitational and electrostatic forces and fields (Unit 8).
In Unit 8 you have studied gravitational and electrostatic forces, and you
have briefly explored the similarities and differences between these two
forces. Imagine you are going to write a blog post, suitable for a student
preparing to start studying S217, exploring these similarities and difference
in more detail. While researching, you find the following article and need to
evaluate its suitability as source material for your blog post.

Use the PROMPT criteria (Unit 6 Section 4) to evaluate the article with
regard to how well it conveys ideas about gravitational and electrostatic
forces, and their similarities and differences.
You should present your PROMPT evaluation as a table using the
template provided here. For each of the PROMPT criteria, other than
the Provenance criterion, you should give a short explanation of the reason
for your evaluation (bullet points are sufficient). The Provenance criterion
has already been completed to give you an indication of the sort of
statements that are required. It is likely that you will need to write more for
your evaluation of some criteria than others; the template indicates how
many marks are available for your evaluation of each criterion.
In addition, two marks are available for the clarity of your answer to
Question 5

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