Particles, Quantum Phenomena and Electricity 1

Apparatus required for each candidate: • a metre ruler rulers with 2 scales may have one of these taped over • about 1.1 mof 42 swgnichrome resistance wire; this should be free from kink

Physics PHA3/B3/XTN

(Specifications A and B)

Unit 3 Investigative and Practical Skills in AS Physics

Route X Externally Marked Practical Assignment (EMPA)

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.

June 2015

For Section A Task 1, Question 1

Candidates are to determine the resistance per metre of nichrome resistance wire

Place the resistance wire along the graduated face of the metre ruler

Wrap approximately 50 mmaround an end of the ruler using the method shown below

Secure the wire using two pieces of insulation tape at both ends to leave about 900 mmof 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

Apparatus required for each candidate:

• a metre ruler (rulers with 2 scales may have one of these taped over)

• about 1.1 mof 42 swgnichrome resistance wire; this should be free from kinks and taped along the graduated face of the metre ruler as described below

• 6 Vdc power supply, eg four 1.5 VD-type dry cells in holder; the positive terminal of the supply should be a 4 mmround socket labelled ‘socket’

• digital voltmeter, or a 31⁄2digit LCD multimeter, capable of reading to 0.01 Vor better: maximum

pd to be read will not exceed 6 V

• digital milliammeter, or a 31⁄2digit LCD multimeter, capable of reading to 1 mAor to 0.1 mA: maximum current to be read will not exceed 100 mA

• 470 Ωlinear 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 mmto 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 4 mmround 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

wire along the graduated face of the ruler

about 50 mm wire wrapped around the end of the ruler

side view

top view

930 940 950 960 970 980 990

insulation tape wound width-ways

around the ruler so the free end

of wire on underside is secured

950 960 970 980 990

insulation tape wound around the end of the ruler so only the wire along the graduated face is exposed

950 960 970 980 990

The apparatus should be set up for candidates as shown in the diagram.

The diagram below explains how the fixed copper contact is secured using the bulldog clip

Once assembled, place the apparatus on the bench in full view

Examiners require no information for this question.

bulldog clip to apply pressure

to copper foil ensuring good contact with wire

rectangle of copper foil laid over wire in approximately the position shown

crocodile clip

900

about 1.1 m 42 swg nichrome resistance wire taped to a metre ruler (about 900 mm of the wire is exposed)

clip attached to a fixed copper contact

bulldog clip securing fixed copper contact

clip attached to a

free copper contact

4 mm round plug

4 mm round socket

470Ω linear

V mA

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

For Section A Task 1, Question 2

Candidates will use the circuit from question 1 to investigate a resistor network

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 2 of the question Ensure that the legs of Xare sufficiently exposed to allow for the

connection of the clips; Centres may also wish to tape over the legs of Yto 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

2 (a) (ii) I1= 10.2 mA, V1= 0.85 V

2 (a) (iii) I2= 10.6 mA, V2= 0.69 V

Apparatus required for each candidate:

• as described for question 1 except for the metre ruler arrangement with its copper contacts and resistance wire

• resistors of resistance 82 Ωand 220 Ω, (all 0.5 Wor 0.6 Wcarbon 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’

220 Ω, value concealed and labelled ‘Y’

switch labelled ‘S’ with on and off positions marked

For Section A Task 2

Candidates will investigate the characteristics of a system consisting of seven springs and a variable mass

Refer to the diagram below and the instructions on page 6 before assembling the apparatus

wire loop B

wire loop T

suspended beam

wire loop secured to the beam using insulation tape

set of three coupled springs attached to the beams using wire loops

thread

spring connected between beams by lengths of thread

clamped horizontal beam (stands not shown)

set of three coupled

springs attached to the

beams using wire loops

wire loop secured to the beam using insulation tape

thread clamp clamp

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 5 N) before use

• additional expendable steel spring with about 300 mmstout thread fastened to each end

• metre ruler and plumb line (no set-square should be provided)

• mass hanger of mass 100 gand eight 100 gslotted masses to give a total mass of 900 gin

100 gincrements

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

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 mmgraduations 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 mmso 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 5

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 Tand wire loop B

Attach the 100 g mass hanger to wire loop Band adjust the position of Buntil the suspended beam

is horizontal, as shown in Figure 5 of the question Adjust the position of loop Tso that it is vertically above B Then add three 100 gslotted 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 gmass 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 mthat lies between 400 gand 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.

cut here loop

General Certificate of Education

June 2015

Advanced Subsidiary Examination

PHYSICS

(SPECIFICATIONS A AND B) PHA3/B3/XTN

Unit 3

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 1

Question 1 No information is required

Section A Task 1

Question 2 No information is required

Section A Task 2

Question 1 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.

her use only

The following instructions include the tasks that candidates will be required to complete in Section A Task 1 and Section A Task 2 These instructions do not include all questions that may be asked

Section A Task 1

1 You are to determine the resistance per metre of a resistance wire using the circuit in

Figure 1.

Figure 1

1 (a) Connect the plug to the socket

Hold the free copper contact firmly on the resistance wire so there is about 0.8 mof 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

1 (a) (i) Determine and record the length laof the wire connected between the contacts

1 (a) (ii) Read and record the current Iain the wire and the potential difference (pd) Vaacross the

wire

clip attached to a fixed copper contact

bulldog clip securing fixed copper contact

resistance wire taped to metre ruler

clip attached to a

free copper contact

plug

socket variable

resistor

V mA

her use only

1 (b) Move the free contact so there is about 0.2 mof 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

1 (b) (i) Determine and record the length lbof the wire now connected between the clips

1 (b) (ii) Read and record the current Ibin the wire and the pd Vbacross the wire

When you have completed parts (a) and (b) remove the plug from the socket.

Unclip the two crocodile clips from the copper contacts and place these and the resistance wire arrangement to one side.

her use only

2 You are to investigate a circuit containing resistors Xand Yof unknown resistance and

a switch S

Connect the circuit consisting of Xand Yso that the clips are attached directly to the

ends of X, as shown in Figure 2.

Figure 2

2 (a) (i) With Sin the off (open) position, connect the plug to the socket

Adjust the variable resistor until the current in the circuit is a minimum.

2 (a) (ii) Read and record in Table 1 the current I1and potential difference V1

2 (a) (iii) Without adjusting the variable resistor, turn Son

Read and record in Table 2 the current I2and potential difference V2

2 (a) (iv) Turn Soff

Adjust the variable resistor so that the current in the circuit increases

Using the procedure as before obtain new values of I1and V1and of I2and V2

Continue until you have five sets of readings.

Disconnect the plug from the socket.

clip clip X

plug

socket variable

resistor

Y S

V mA

her use only

Section A Task 2

1 You are to investigate the spring system shown in Figure 4.

Figure 4

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 Tand B The loops can slide along both beams between the coupled

springs

1 (a) Attach the 100 gmass hanger to wire loop B

Adjust the position of Buntil the suspended beam is horizontal

Adjust the position of Tuntil it is vertically above Band the apparatus appears as shown

in Figure 5, on page 3.

wire loop B

wire loop T

suspended beam

clamped horizontal beam

clamp

clamp

her use only

Figure 5

1 (b) (i) Record m, the total mass supported from wire loop B

1 (b) (ii) Measure and record y, the vertical distance between the top of the clamped beam and

the top of the suspended beam.

1 (c) You are to make suitable measurements to determine values of ythat correspond to

different values of m

You are provided with additional slotted masses

Add these masses, in turn, to the mass hanger so that mincreases 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 Tso that it remains vertically above B

y

mass hanger

position of wire loop B

adjusted until suspended beam is horizontal

position of wire loop T

vertically above wire loop B