Particles, Quantum Phenomena and Electricity 1

General Certificate of Education Advanced Subsidiary Examination June 2015 Physics PHA3/B3/XTN (Specifications A and B) Unit Investigative and Practical Skills in AS Physics Route X Externally Marked Practical Assignment (EMPA) Teachers’ Notes Confidential The Exams Officer should make two copies of these Teachers’ Notes; one copy for the Head of A-level Physics and one for the technician These copies can be released to the Head of A-level Physics and the technician at any point following publication but must be kept under secure conditions at all times Teachers can have sight of the Teachers’ Notes but no further copies should be made Estimated entries must be submitted to AQA in order for centres to receive hard copies of the materials to be used for candidates WMP/Jun15/PHA3/B3/XTN/E5 PHA3/B3/XTN For Section A Task 1, Question Candidates are to determine the resistance per metre of nichrome resistance wire Apparatus required for each candidate: • a metre ruler (rulers with scales may have one of these taped over) • about 1.1 m of 42 swg nichrome resistance wire; this should be free from kinks and taped along the graduated face of the metre ruler as described below • V dc power supply, eg four 1.5 V D-type dry cells in holder; the positive terminal of the supply should be a mm round socket labelled ‘socket’ • digital voltmeter, or a 31⁄2 digit LCD multimeter, capable of reading to 0.01 V or better: maximum pd to be read will not exceed V • digital milliammeter, or a 31⁄2 digit LCD multimeter, capable of reading to mA or to 0.1 mA: maximum current to be read will not exceed 100 mA • 470 Ω linear potentiometer; this could be fitted with a pointer knob if that is the usual practice in the Centre • two rectangles of copper foil of dimensions approximately 30 mm × 20 mm to form the free and fixed copper contacts; ensure copper foil is clean • bulldog clip to secure fixed copper contact • insulation tape • suitable connecting leads to include: • one flying lead terminating at a mm round plug labelled ‘plug’ to serve as a means of connecting the circuit to the power supply • two crocodile clips joined to flexible leads of sufficient length to enable the procedure described in the question to be carried out Place the resistance wire along the graduated face of the metre ruler Wrap approximately 50 mm around an end of the ruler using the method shown below wire along the graduated face of the ruler side view about 50 mm wire wrapped around the end of the ruler top view 930 940 950 960 970 980 990 Secure the wire using two pieces of insulation tape at both ends to leave about 900 mm of exposed wire running along the graduated face of the ruler No other part of the wire should be visible to the candidate The method to be used is illustrated below 950 960 970 980 990 insulation tape wound width-ways around the ruler so the free end of wire on underside is secured WMP/Jun15/PHA3/B3/XTN 950 960 970 980 990 insulation tape wound around the end of the ruler so only the wire along the graduated face is exposed The apparatus should be set up for candidates as shown in the diagram mm round plug mA 470 Ω linear mm round socket V clip attached to a free copper contact clip attached to a fixed copper contact about 1.1 m 42 swg nichrome resistance wire taped to a metre ruler (about 900 mm of the wire is exposed) bulldog clip securing fixed copper contact The diagram below explains how the fixed copper contact is secured using the bulldog clip crocodile clip rectangle of copper foil laid over wire in approximately the position shown 900 bulldog clip to apply pressure to copper foil ensuring good contact with wire Once assembled, place the apparatus on the bench in full view Examiners require no information for this question Turn over ᮣ WMP/Jun15/PHA3/B3/XTN The following data is provided to assist in trialing the practical tasks Q1 la = 0.800 m Ia = 20.3 mA Va = 2.34 V WMP/Jun15/PHA3/B3/XTN For Section A Task 1, Question Candidates will use the circuit from question to investigate a resistor network Apparatus required for each candidate: • as described for question except for the metre ruler arrangement with its copper contacts and resistance wire • resistors of resistance 82 Ω and 220 Ω, (all 0.5 W or 0.6 W carbon or metal film) wired in a continuous loop with a switch (to be labelled S), as shown on the diagram below; the switch should have the open/off and closed/on positions marked and the resistance of these resistors must be concealed from the candidates • insulation tape 82 Ω, value concealed and labelled ‘X’ switch labelled ‘S’ with on and off positions marked 220 Ω, value concealed and labelled ‘Y’ Construct the circuit as shown above and place the apparatus on the bench in full view Note that the candidates will be instructed to attach the clips directly to the ends of X, as shown in Figure of the question Ensure that the legs of X are sufficiently exposed to allow for the connection of the clips; Centres may also wish to tape over the legs of Y to prevent connection of the clips in the wrong position Examiners require no information for this question The following data is provided to assist in trialing the practical tasks (a) (ii) I1 = 10.2 mA, V1 = 0.85 V (a) (iii) I2 = 10.6 mA, V2 = 0.69 V Turn over ᮣ WMP/Jun15/PHA3/B3/XTN For Section A Task Candidates will investigate the characteristics of a system consisting of seven springs and a variable mass Apparatus required for each candidate: • two half-metre rulers or equivalent narrow wooden laths; these will be referred to in the question as the ‘horizontal beam’ and the ‘suspended beam’ • six wire loops; these can be fashioned from large paperclips, eg length about 50 mm, larger width about 10 mm, as described below or alternatively thin copper wire could be used • insulation (or ‘gaffer’) tape to secure the positions of the loops that are joined to the ends of both sets of three coupled springs • two retort stands fitted with boss and clamp; stands with small bases may need a counterweight or be G-clamped to the bench • two sets of three expendable steel springs coupled together; if new springs are to be used these should be briefly placed under tension (eg of about N) before use • additional expendable steel spring with about 300 mm stout thread fastened to each end • metre ruler and plumb line (no set-square should be provided) • mass hanger of mass 100 g and eight 100 g slotted masses to give a total mass of 900 g in 100 g increments Refer to the diagram below and the instructions on page before assembling the apparatus clamp clamped horizontal beam (stands not shown) wire loop secured to the beam using insulation tape clamp wire loop T thread set of three coupled springs attached to the beams using wire loops set of three coupled springs attached to the beams using wire loops wire loop secured to the beam using insulation tape suspended beam spring connected between beams by lengths of thread WMP/Jun15/PHA3/B3/XTN thread wire loop B Suitable wire loops can be fashioned by cutting the paperclips with pliers at the point shown in the left-hand view to produce the loop in the right-hand view cut here loop Slide three loops over each of the beams Note that some paper clips have squared-off ends and if so, it is suggested that all the clips joined to the horizontal beam should have the squared-off end at the top The outer clips joined to the suspended beam should have the squared-off end at the bottom while the central clip (from which the mass hanger will later be suspended) should have the squared-off end at the top Ensure that the beam to be clamped is horizontal and that it projects over the edge of the bench so the suspended beam hangs freely above the floor, then secure the arrangement Suitable counterweights or G-clamps may be required to guarantee stability The horizontal separation of the wire loops at the top of each set of coupled springs should be 300 mm If a half-metre ruler is used for this beam the loops should be positioned at the 100 mm and 400 mm graduations on the ruler The loops at the bottom of the sets of coupled springs should be equidistant from the centre of the supported beam and the horizontal separation should be 300 mm so that the sets of springs are parallel along their length Once correctly positioned secure these loops to their respective beams using insulation tape or similar, as illustrated in the diagram on page The remaining two loops should be positioned so each can slide freely along their respective beam between the two points of attachment of the coupled springs These loops are referred to in the question as wire loop T and wire loop B Attach the 100 g mass hanger to wire loop B and adjust the position of B until the suspended beam is horizontal, as shown in Figure of the question Adjust the position of loop T so that it is vertically above B Then add three 100 g slotted masses to the hanger Tie a free end of one of the threads that is attached to the additional spring to wire loop T, adjusting the length connecting the spring to the loop until this is about 150 mm Pass the free end of the thread suspended from the single spring through loop B, and without pulling the thread so tight that the coils open in the central spring, tie the thread off loosely Add another 100 g mass to the hanger and check that this additional load causes the coils in the central spring to open, thereby increasing the stiffness of the spring system for a value of m that lies between 400 g and 500 g Remove this extra mass to confirm that the coils in the central spring close as before, then tie off securely Place the additional apparatus on the bench in full view Examiners require no information for this question Turn over ᮣ WMP/Jun15/PHA3/B3/XTN General Certificate of Education June 2015 Advanced Subsidiary Examination PHYSICS (SPECIFICATIONS A AND B) PHA3/B3/XTN Unit SUPERVISOR’S REPORT When completed by the Supervisor, this Report must be attached firmly to the attendance list In the case of any problem affecting a particular candidate, a copy of this report should be attached to the candidate’s script, before despatch to the Examiner Information to be provided by the centre Section A Task Question No information is required Section A Task Question No information is required Section A Task Question No information is required Details of problems encountered by candidate candidate number Supervisor’s Signature Centre Number Date Centres may make copies of this Supervisor’s Report for attachment to individual scripts where necessary WMP/Jun15/PHA3/B3/XTN The following instructions include the tasks that candidates will be required to complete in Section A Task and Section A Task These instructions not include all questions that may be asked Section A Task 1 You are to determine the resistance per metre of a resistance wire using the circuit in Figure Figure plug mA socket V clip attached to a free copper contact on ly variable resistor Te ac he ru se resistance wire taped to metre ruler clip attached to a fixed copper contact bulldog clip securing fixed copper contact (a) Connect the plug to the socket Hold the free copper contact firmly on the resistance wire so there is about 0.8 m of wire between the free and fixed contacts Without moving the free contact, adjust the setting of the variable resistor until the current in the circuit is about 20 mA (a) (i) Determine and record the length la of the wire connected between the contacts (a) (ii) Read and record the current Ia in the wire and the potential difference (pd) Va across the wire Turn over ᮣ WMP/Jun15/PHA3/B3/XTN 10 (b) Move the free contact so there is about 0.2 m of resistance wire between the free and fixed contacts Without moving the free contact adjust the setting of the variable resistor until the current in the circuit is once again about 20 mA (b) (i) Determine and record the length lb of the wire now connected between the clips (b) (ii) Read and record the current Ib in the wire and the pd Vb across the wire When you have completed parts (a) and (b) remove the plug from the socket Te ac he ru se on ly Unclip the two crocodile clips from the copper contacts and place these and the resistance wire arrangement to one side WMP/Jun15/PHA3/B3/XTN 11 You are to investigate a circuit containing resistors X and Y of unknown resistance and a switch S Connect the circuit consisting of X and Y so that the clips are attached directly to the ends of X, as shown in Figure Figure plug mA socket variable resistor clip X S on ly V clip Te ac he ru se Y (a) (i) With S in the off (open) position, connect the plug to the socket Adjust the variable resistor until the current in the circuit is a minimum (a) (ii) Read and record in Table the current I1 and potential difference V1 (a) (iii) Without adjusting the variable resistor, turn S on Read and record in Table the current I2 and potential difference V2 (a) (iv) Turn S off Adjust the variable resistor so that the current in the circuit increases Using the procedure as before obtain new values of I1 and V1 and of I2 and V2 Continue until you have five sets of readings Disconnect the plug from the socket Turn over ᮣ WMP/Jun15/PHA3/B3/XTN 12 Section A Task You are to investigate the spring system shown in Figure Figure clamp wire loop T clamp Te ac he ru se suspended beam on ly clamped horizontal beam wire loop B The suspended beam is supported from a clamped horizontal beam by two sets of three coupled springs Do not move or adjust the clamps Another spring has been connected between the beams by pieces of thread joined to wire loops T and B The loops can slide along both beams between the coupled springs (a) Attach the 100 g mass hanger to wire loop B Adjust the position of B until the suspended beam is horizontal Adjust the position of T until it is vertically above B and the apparatus appears as shown in Figure 5, on page WMP/Jun15/PHA3/B3/XTN 13 Figure position of wire loop T vertically above wire loop B Te ac he ru se on ly y position of wire loop B adjusted until suspended beam is horizontal (b) (i) mass hanger Record m, the total mass supported from wire loop B (b) (ii) Measure and record y, the vertical distance between the top of the clamped beam and the top of the suspended beam (c) You are to make suitable measurements to determine values of y that correspond to different values of m You are provided with additional slotted masses Add these masses, in turn, to the mass hanger so that m increases in several stages until all the masses have been used As each additional mass is added make any necessary adjustment to the position of B to keep the suspended beam horizontal and adjust the position of T so that it remains vertically above B Copyright © 2015 AQA and its licensors All rights reserved WMP/Jun15/PHA3/B3/XTN