Particles, Quantum Phenomena and Electricity 2

Apparatus required: • two expendable steel springs, coupled together • mass hanger of mass 100 g; five additional 100 gslotted masses • concealed mass labelled ‘mass U’ consisting of a m

WMP/Jun14/PHA3/B3/XTN/E8 PHA3/B3/XTN

June 2014

(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 by candidates.

For Section A Task 1, Question 1

Candidates are to investigate the extension of a mass-spring system Having calibrated the springs, they are to incorporate these in a system of coplanar forces to determine the value of an unknown mass

Link one end of the coupled springs through the arm of the clamp before fitting this to the boss, thus ensuring that the springs cannot slip off Set the height of the clamp at about 300 mmabove the bench with the arm of the clamp perpendicular to the edge of the bench Use a G-clamp to secure the base of this stand to the bench Candidates are instructed not to move this stand or adjust the height of the clamp to which the springs are attached

Tie the string to the free end of the springs then fasten a small loop about 8 cmfrom this point Make an ink mark on the string at roughly the midpoint of the string between the spring and the loop Pass the string over the pulley then fasten the mass hanger securely to the free end Candidates are instructed not to unfasten the string from the mass hanger and Supervisors should be vigilant that they adhere to this

Cut the sheet of paper into two lengthways and arrange the piece end to end to create a strip of about 100 mmwide and 580 mm long Tape or Blu-Tack this to the bench so that it will lie below the horizontal part of the string during part (a) of the experiment

Arrange the apparatus as shown below and place all the other equipment on the bench in clear view

of the candidate

Apparatus required:

• two expendable steel springs, coupled together

• mass hanger of mass 100 g; five additional 100 gslotted masses

• concealed mass labelled ‘mass U’ consisting of a mass hanger and slotted masses to total

340 g; the hook of the mass hanger should be accessible so that the mass can be suspended from the loop on the string

• retort stand to be fitted with a boss about 300 mm above the bench to which a clamp is fixed; the base should be made secure with a G-clamp

• retort stand to be fitted with a boss, the height of which can be adjusted up to 500 mmabove the bench; a free-running pulley is to be fixed to this boss so that the axis of rotation of the pulley is parallel to the bench – it is suggested that a counterweight (or other means) be

provided to prevent this stand from sliding or toppling when candidates carry out

question 1 (a)(iii)

• about 600 mmof string

• half metre ruler and set-square

• one sheet of A4 plain paper; Sellotape or Blu-Tack as required to stick this to the bench

• pencil

clamp L

stand L

loop

stand R

boss R

ink mark on the string

G-clamp not shown

mass hanger counterweight

not shown

The following data are provided to assist in trialling the practical tasks.

Question 1

1 (a) (i) h/ mm= 270

1 (a) (iv)

1 (d) (i) xU/mm= 141

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For Section A Task 2

Candidates will investigate how the pd across a power supply varies when the resistance of the external circuit is changed

The circuit, which should be connected ready for each candidate, is shown below

The 10 Ωresistor should be wired in series with the positive terminal of the power supply; the resistor should then be concealed from view, eg by positioning it alongside the cell holder and winding insulation tape around it

Apparatus required for each candidate

for the circuit:

• digital voltmeter, or a 3½ digit multimeter, capable of reading to 0.01 Vor better

• two connecting leads terminating at 4 mm plugs to connect the voltmeter in the circuit

• dc power supply, one or more dry cells in holder are adequate, pd at discretion of centre to suit the range of voltmeter to be provided (a single D-type cell in a holder is suitable if the voltmeter

is set for full scale reading of 2 V/ 2000 mV)

• 10 Ωresistor (0.5 Wor 0.6 W, carbon or metal film) should be wired in series with the positive terminal of the power supply; to avoid confusion this resistor should be concealed from the view

of the candidate

• two 4 mmround sockets labelled ‘P’ and ‘N’ to be connected to the free end of the 10 Ωresistor and the negative terminal of the dc power supply respectively (see circuit diagram below)

• one 120 Ωresistor (0.5 Wor 0.6 W, carbon or metal film) the value of this resistor is to be concealed from the candidate; this resistor should be labelled ‘resistor X’ and placed in clear view for the candidate to see

• resistors of resistance 39 Ω, 68 Ωand 47 Ω, (all 0.5 Wor 0.6 W, carbon or metal film) wired in series, as per the diagram below

• SPST switch, toggle type, labelled ‘S’ with ‘open’ and ‘closed’ positions marked

• two short leads terminating at crocodile clips to serve as flying leads (see diagram and

explanation below); these leads should be made using insulated stranded wire, not solid-core wire

• strip-board, solder pins and connecting wire, as required to complete the connection of the

10 Ω resistor in series with the positive terminal of the power supply

for construction of the mounted resistors:

• terminal block: four 2-way terminal blocks (eg cut from 2 A or 3 A 12-way terminal block)

• 4 screws

• rectangular piece of softwood on which to mount circuit

round socket labelled P

round socket labelled N

47 Ω

concealed

10 Ω resistor

68 Ω

39 Ω

switch S

flying lead flying lead

The mounting of the resistors and flying leads can be accomplished using the 2-way terminal

blocks, screwed to a rectangular piece of softwood, as shown in the diagram below Labels,

showing the values of the resistors, can be stuck on the wood, as shown

The length of the flying leads should enable each lead to be connected across (and thus shorting out) the resistor to either side so that between sockets Pand Na series circuit with any permutation

of the 39 Ω, 68 Ωand 47 Ωresistors can be produced

Note that it is not possible to use the flying leads to short out all three resistors simultaneously and

no additional leads should be made available that might enable the candidate to do this

Candidates will vary the external resistance of the circuit by using the flying leads singly or in combination

For example, when one flying lead is connected across the 47 Ωresistor the external resistance between sockets Pand Nis a series combination of 39 Ωand 68 Ω The candidates will be

expected to deduce that the circuit resistance for this circuit is 107 Ω; the Supervisor must not

provide the candidates with any assistance in making this deduction

47 Ω

68 Ω

39 Ω

flying lead connected in parallel with the 47 Ω resistor

39 Ω 68 Ω 47 Ω

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The candidates will also be required to connect resistor X in parallel with the 68 Ωresistor This can

be achieved using both the flying leads, eg

Testing:

With Sopen the voltmeter should read the emf of the supply

When Sis closed and resistor X is in parallel with the 68 Ωresistor as shown above, the voltmeter reading will fall such that the ratio, –––––––––––––––––––––––––– is between 1.06 and 1.10

Examiners require no information for this question.

The following data is provided to assist in trialling the practical tasks

Question 1

1 (a) (i) ε/ V= 1.528

1 (a) (ii) VX/V= 1.411

1 (b)

voltmeter reading with Sopen voltmeter reading with Sclosed

47 Ω

68 Ω

39 Ω

resistor X

R1+R2+R3 in series 154 1.428

General Certificate of Education

June 2014

Advanced Subsidiary Level 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, or in the case of any problem affecting a particular candidate, it should be attached to the candidate’s script, before despatch to the Examiner.

Information to be provided by the centre

Section A Task 1

Section A Task 2

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

Section A Task 1

1 You are to investigate the extension of a mass-spring system

1 (a) You are provided with the apparatus shown in Figure 1.

Figure 1

Stand Lhas been clamped to the bench and a mass hanger has been securely

fastened to the free end of the string

An ink mark has been made on the string between the end of the spring and the loop tied in the string

You must not move stand L, or adjust the height of clamp L, or unfasten the string from the mass hanger during the experiment.

clamp L stand L

loop

stand R

boss R

ink mark on the string

G-clamp not shown

mass hanger counterweight

not shown

her use only

WMP/Jun14/PHA3/B3/XTN

1 (a) (i) Add mass to the hanger so that m, the total mass fastened to the string, is 200 g

Move stand Rto the right until the hanger is lifted clear of the bench

Adjust the height of boss Runtil the part of the string between the spring and the pulley

is horizontal, as shown in Figure 2.

Check that the system is in equilibrium

Figure 2

Measure and record h, the vertical distance between the horizontal part of the string and the table

h =

1 (a) (ii) A point has been marked on the string between the end of the spring and the loop; a

strip of paper has been taped to the bench below the horizontal part of the string

Mark the point Oon the strip of paper directly below the ink mark

Question 1 continues on the next page

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point O

marked on the strip of paper

loop

boss R

ink mark

h

m = 200 g

her use only

1 (a) (iii) Add mass to the hanger until m = 600 g.

Without adjusting the height of boss R, move stand Rfurther to the right until the

mass is once again lifted clear of the bench, as shown in Figure 3.

Figure 3

Check that the system is in equilibrium, then mark the point Pon the strip of paper directly below the ink mark

Mark a straight line joining the points Oand P

Measure and record x, the distance along the line between Oand P

x =

1 (a) (iv) Remove mass from the hanger so that m = 500 g.

If necessary move stand Rto the left so that the hanger does not touch the pulley, while remaining clear of the bench

Check that the ink mark is directly above the line between Oand P

Check that the system is in equilibrium then locate the point on OPthat is directly below the ink mark then measure and record the new value of x

Repeat the procedure until you have the values of xwhen m = 400 gand m = 300 g

Record all your measurements in Table 1 on page 6.

position of point O

mark P

marked on the strip of paper

boss R

at same height

stand R

moved to the right

ink mark

m = 600 g

x

her use only

WMP/Jun14/PHA3/B3/XTN

Measurements

Table 1

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200 600 500 400 300

her use only

1 (d) You are provided with an object U, the mass of which you are to find

Suspend Ufrom the loop tied in the string

The apparatus will now appear as in Figure 5.

Figure 5

Add mass to the hanger so that m = 500 g

Raise boss Rso that both masses are lifted clear of the bench and the part of the string between the spring and the loop is approximately horizontal

Make small adjustments to the position of stand R, moving this stand either left or right, until the ink mark is at a height h, as measured in part (a)(i), and is directly over the line between Oand P, as shown in Figure 6.

Figure 6

object U

suspended from the loop

boss R

at same height

as before ink mark

position of point O

point marked on line between O and P

directly below the ink mark

boss R raised and stand R

moved to the left

or to the right,

as required ink mark

position of point P

object U

m = 500 g

h

xU

1 (d) (i) Check that the system is in equilibrium then locate the point between Oand Pthat is

directly below the ink mark

Measure and record the distance xUthat is defined in Figure 6.

xU=

Turn over䊳

Teac

her use only

her use only

Section A Task 2

1 In this experiment you are required to investigate how the potential difference (pd)

across a power supply varies when the resistance of the external circuit is changed

You are provided with the circuit shown in Figure 8.

Figure 8

1 (a) Use the leads supplied to connect the voltmeter between socket Pand socket N

1 (a) (i) Ensuring that switch S is in the open (off) position, read and record the voltmeter

reading ε, which is the electromotive force (emf) of the power supply

ε =

P N

47 Ω

68 Ω

39 Ω

switch S

flying lead flying lead

her use only

WMP/Jun14/PHA3/B3/XTN

1 (a) (ii) You are provided with a resistor X, the resistance of which has been concealed

Use the flying leads to connect resistor Xin parallel with the 68 Ωresistor, as shown in

Figure 9.

Figure 9

Close (turn on) switch Sthen read and record Vx, the new voltmeter reading

Vx=

Turn over䊳

47 Ω

68 Ω

39 Ω

resistor X

her use only

1 (b) Keeping switch Sclosed, remove resistor Xso that R, the resistance of the circuit

between socket Pand socket N, is the series combination of the 39 Ω, 68 Ωand 47 Ω

resistors

You may assume that each flying lead has zero resistance so these can be used

individually, or in combination, to change Rin a predictable way

In the example shown in Figure 10, one flying lead has been connected in parallel with

the 47 Ωresistor and Ris now the series combination of the 39 Ω and 68 Ωresistors

Figure 10

Using neither of the leads, or either lead separately or both leads in combination, obtain values of Vthat correspond to all possible values of R.

When you have completed your measurements, open (turn off) switch S

Record below all your values of Rand Vin a single table

Note that the independent variable should be recorded in the left-hand column of your

table

47 Ω

68 Ω

39 Ω

the flying lead is shorting out the

47 Ω resistor