Planning 2010 (9760/4)

This planning question is for private candidate sitting for A level Cambridge Nov of 2010. Here is my suggested answer.

Planning_2008_Q1_9702

Here is a mark scheme from the website: www.cie.org.uk
Nov 08 Paper 5 (9702)
1 A student wishes to investigate how the resistance R of a light-dependent resistor varies with the distance d from an intense light source.
It is believed that the relationship between R and d is
R = kdn where k and n are constants.
Design a laboratory experiment to test the above relationship. The light-dependent resistor has a resistance of 100 Ω when it is in bright light and a resistance of 500 kΩ when no light falls on it.
You should draw a diagram showing the arrangement of your equipment. In your account you
should pay particular attention to
(a) the procedure to be followed,
(b) the measurements that would be taken,
(c) the control of variables,
(d) how the data would be analysed,
(e) any safety precautions that you would take.
[15]
Mark Scheme
Planning (15 marks)
Defining the problem (3 marks)
1. d is the independent variable or vary d (allow in table if numbers given) [1]
2. R is the dependent variable or measure R as d varied (allow in table) [1]
3. Keep output of light source constant (allow constant current / e.m.f. / voltage / power) [1]
Methods of data collection (5 marks)
4. Diagram showing an LDR in a circuit and an independent lamp. [1]
5. Diagram showing ruler measuring appropriate distance or d labelled correctly. [1]
6. Correct circuit diagram for LDR using conventional symbols; allow labelled diagram [1]
• Ammeter and voltmeter with power supply,
• or potential divider methods
• ohmmeter without power supply,
• or bridge methods.
7. Method of determining R. [1]
• Ohmmeter.
• R = V/I justified.
• Potential divider equation
• Description of balancing bridge with correct equation.
8. Perform experiment in a dark room/tube [1]
Method of analysis (2 marks)
9. Plot a graph of log R against log d [1]
10. Relationship is correct if log R against log d graph is a straight line [1]
Safety considerations (1 mark)
11. Do not look directly at bright light source / do not touch hot light source. [1]
Allow safety glasses with reference to light source.
Additional detail (4 marks)
• Detail on measuring the distance
• Keep orientation of LDR with respect to the light source constant
• Reasoned method for keeping light and LDR in correct orientation. (E.g. use of set square,fix to rule, optical bench or equivalent)
• Determination of a typical current
• Range of ammeter / ohmmeter
• Control (or monitoring) of an additional variable e.g. temperature
• Reason for performing experiment in a dark room related to the LDR
• Method for checking the output of the light source is constant.
• Identifies gradient = n and/or y-intercept = log k for log R against log d graph
• Do not allow parallax when reading ruler, or reflectors.
Mark scheme published in website : http://www.cie.org.uk/qualifications/academic/uppersec/alevel/subject?assdef_id=758
[Total: 15]

Planning_2005_Q1

Planning Question :November 05 Q1
To investigate how the deflection of a stream of water depends on the electric field strength keeping the flow rate constant.
Diagram :
DC supply to 2 parallel plates clamped with insulated clamps and retort stand . Voltmeter connected across the plates(note : mistake on the diagram for voltmeter) .A stream of water could be supplied from burette connected to water supply.

Procedure :
1 Set up circuit as shown in diagram. Turn on the DC supply keeping the voltage constant . Record the reading of the voltmeter V and measure the distance between the plates d using a ruler.
2. Calculate the electric field strength E using the formula E= V/d
3. Turn off the DC supply and turn on the burette tap . Measure the position of the water stream y1using the traveling microscope scale. Turn on the DC supply and measure the new position of the water stream y2. Turn Off the DC supply.
4. Calculate the deflection y using the formula y = y2-y1.
5. Repeat steps 1 to 4 by varying the distance d to obtain 6 sets of E and y.
6. Plot a graph of lg y vs lgE assuming the equation y = kE*. If the graph is linear the equation is valid and the gradient is * and the intercept c = lg k.

Reliability and precaution :
1 The flow rate is kept constant by ensuring that the water in the burette is always at the same level and the tap fully open.
2. The parallel plate is kept at equidistant apart at the top and the bottom using clamps at the top and bottom of the plates.
3. Voltage of the DC supply is maintained by always checking the voltmeter.
4. Take repeated readings of the traveling microscope scale and obtains the average y.
5. The jet of water should be kept very small so that the point of reference of the stream is easily located when viewed from traveling microscope.
6. Use sufficiently long parallel plates and keep the water stream at the centre between the two plates.
7. The traveling microscope is positioned to measure the same location of the stream of water throughout the experiment.

Planning_2005_Q2

Planning_2000_Q3

To investigate how the length of the wire made of lead changes with time as temperature and the load which it supports are changed.

Diagram: Draw a long box. The lead wire hangs from the ceiling support. A load is used to keep the wire taut. A heater (box) is placed at the bottom and connected to power supply. A ruler with with vernier scale is placed along side the wire to measure length. A thermostat is placed in in series with heater to maintain constant temperature. A thermometer is placed in the box with holder.

Procedure:
1.Set up the lead wire in the box as shown above.
2.Turn on the heater and record the temperature of the air in the box using a thermometer when it is steady. Keep the temperature constant with the adjustment made at the thermostat with heater.
3. Place slotted masses at the end of the wire and record the total mass of the slotted masses.
4. Measure the length of the wire using a ruler with verneir scale attached . Use a stopwatch to measure time and record the length regularly with time.
5. Obtain 8 sets of length and time keeping the load and temperature constant .
6. Repeat steps 2 to 5 by varying the temperature of the air around the wire in the box.
7. Repeat steps 2 to 5 by varying the load used to stretch the wire.

Reliability :
1. Use a long wire so that the extension is significantly large.
2 Measure the diameter of the wire at several places to check of uniformity.
3 measure the extension over a long period of time.
4 Use a kink free wire.
Precauation:
1 Wear goggles when handling the wire to protect the eye if the wire breaks suddenly.
2. Use gloves to handle the apparatus in the box as it is hot.

Design flow chart

Strategy 1: Variable Y vs Variable X (lifted from question) X is independent and Y is dependant keeping z constant.
Diagram: Schematic box like diagram only . Do not copy diagram again. ....[2]
Strategy 2 : What and how to measure the variables X.(instrument and method used)[2]
Strategy 3: What and how to measure the variable Y. (instrument and method used)[2]
Strategy 4: Repeat steps ....by varying X to obtain 6 sets of readings of X and Y .[1]
Strategy 5. Plot a graph of lg Y vs lg X . If the graph is linear.... valid ... n = gradient and intercept =....[1]

Reliability: Repeat the measurement of Y to obtain the average reading of Y
Some other constant of variables to be mentioned here .[2]
Safety precaution:

Design question_Asp_24sept

Marks are awarded here:
1. Signal generator connected to loudspeaker
2. Microphone connected to CRO
3. Output measured for various frequencies
4. Output determined by size of peak on CRO
5. CRO used to measure frequency
6. Experiment performed away from external noise
7. Use of CRO to measure frequency (one more marks possible if period T and time base is mentioned )
8 Distance from loudspeaker to microphone constant
9. Monitor output from signal generator and keep output (amplitude)constant.
The signal generator output(amplitude) also needs the be monitored using the CRO.
The marks above are awarded by examiner and hence this is what i would present in report .

Aim : To investigate how the output of a microphone varies with the freq of the sound waves keeping the amplitude of the source constant.
Statement copied from question adding the constant of variable of the greatest importance. Other constant of variables like distance can be mentioned later.
Diagram: Signal generator (box) connected to loudspeaker. Other side , microphone connected to CRO(box) . Lable correctly.No 3D digrams and no values needed.
Procedure:
1. Set up the expt as above.
2. Adjust the signal generator and note the peak voltage of the signal generator. Keep this value constant.
3. Measure the microphone output using the CRO. Record the amplitude Vo by taking note of the y sensitivity of the CRO. Record the period T by taking note of the time base scale of the CRO.
4 Calculate the freq using the formula f= 1/T.
5 Repeat step 2 to 4 by varying the freq of the signal generator to obtain 6 sets of f and Vo.
6. Plot a graph of lg Vo against lg f . Assuming that Vo and f is related by the
equation Vo=kfn.If the graph is linear , the equation is valid and the gradient = n and the intercept = lg k .

Reliability:
Ensure that the distance between loudspeaker and microphone is kept constant.
Ensure that there are no other sources of sound around the microphone.

Planning_2002_Q2

To investiagate how the magnetic flux density B at the centre of a flat coil is directly proportional to the number of turns in the coil.

Diag: Power supply , ammeter , coil , variable resistor in series.

Procedure:
1. Make a coil of N turns using a cylinder of radius r. Connect the circuit as shown.
2. Record the number of turns N. Adjust the variale resistor and note the current I.
3. Using a Hall probe connected to a data logger and computer , record the reading of magnetic flux density B .Ensure the hall probe is placed at the centre of coil.
4. Repeat steps 1 to 3 by varying N, keeping I constant to obtain 6 sets of readings of N and B.
5 Plot a graph of B vs N. A graph of B against N would be linear


Control of variables :
The radius of the coil is constant when N is varied
The current is kept constant by adjusting the variable resistor when N is varied.The ammeter reading should remain constant .

Reliabiltiy :
1. The Hall probe must be placed at the same location at the centre of the oil in the plane of the coil. It is also aligned perpendicular to the plane of the coil. Draw a diagram to shown this orientation.
2. The coil and probe should be kept away from other magnetic fields.
3. The Earth's magnetic field is negligible.

Planning_2002_Q1

To investigate how the vol flow rate depends upon the separation d of threads in the material

Diagram 1: Stretch out a piece of material using clips and retort stand. Using a container the top of the material allow a constant flow of water onto the material. Place a beaker at the bottom of the cloth to collect the water.

Diagram 2: Use a retort stand to hold the laser . Use a holder to stretch out the material in front of the laser. The light that passes through should fall on a screen a distance D away from the material.

Procedure:
1. Set up expt as in Diag 1. Start the stopwatch and replace a clean beaker to collect the water.
2. After a time t, stop the stopwatch and remove the beaker. Record the time interval as shown.
3. Measure the vol of water V collected using a measuring cylinder.
4. Calculate the flow rate by using the formula v = V/t.
5. Repeat steps 1 to 4 by varying the material of different d value.
6. The distance between the threads of the material used , d can be measure by using set up shown in diag. 2
7. Turn off the light and turn on the power of the laser.
8. Stretch the material vertically in front of the laser .
9. Using a ruler , measure the fringe spacing on the screen, keeping the distance D from the laser to the screen constant.The angle can be calc using tan angle formula.
The distance d can be measured using the formula dsin(angle) = n(wavelength) .
10. Repeat steps 7 to 9 by varing the material of different d . Matching the material and the flow rate it yields.
11. Plot a graph of lg v vs lg d . If the graph is linear , the equation v=kdn is valid ......

Control of variables:
1. The height from which the water was dropped should be kept constant .
2. The water falling onto material at a constant rate.
3. The tension on the material should be constant.

Reliability:
Repeat the measurement of fringe separation and averaging the value to calc angle .
Ensure the cloth is dry when used in diffraction expt
Wet the material before starting the volume rate measurement.

SPA Q4_N99

Aim: To investigate how the vol flow rate of a concentrated salt soln depends upon the magnetic field strength, keeping the concentration constant .
Diagram: Do not copy diagram again. Draw a circuit diagram with coil , battery, rheostat and ammeter.
Procedure:
1. Set up the circuit as above.
2. Set the variable resistor to a maximum and measure the magnetic field strength B between the coils using a Hall probe connected to a data logger and computer.
3. Open the tap at the end of the pipe and collect the soln at the start of the stopwatch.
4. Measure the vol of soln v, using a measuring cylinder and time taken, t from the stopwatch.
5. Calculate the vol flow rate V = v /t
6. Repeat steps 2 to 5 by varying the value of B to obtain 6 sets of v and t.
7. Plot a graph of lg B vs lgV assuming the equation is B = kVn . If the graph is linear then equation is valid, the grad = n and intercept = lg k.
8. To investigate the how the flow rate depends on concentration of soln , the B is kept constant.The concentration can be varied by adding more mass of salt into the same amount of water. C = m/vol.

Reliability :
The Hall probe is placed perpendicular to the coil.
The current through the sol is kept oonstant.
The expt is repeated and average value is calc .
Safety :
The current through the coils is large , hence do not touch with bare hands.
Place bricks on retort stand to prevent the apparatus from toppling.,

SPA planning ASP Q 3 RAdioactivity

1 Need draw only one diagram. Just say replace paper with aluminum .
2 absorption by air is not directly measured so got to say count rate C
3 show the two diff values as C1 -C2=C3 where C3 is the count rate due to beta only.
4 handle the source with tongs,do not point the source at anyone and store away source in a lead box when not in use.
5 good design : make sure the source has long half life, high energy beta may still pass through aluminum, the distance d should be measured from the same refrerence point on the GMtube . Repeating measurement and averaging is important in this expt.

SAMPLE
To investigate how the count rate C of beta depends on the distance d between the Source and GM tube keeping the source power constant.

Procedure:
1 Set up the experiment as shown above.
2 Measure the distance d using a ruler.
3.Place a sheet of paper between the source and Gm tube and record the count rate C1 Using the rate meter.
4. Record the count rate C2 when the paper is replaced by an aluminium sheet.
5 The count rate C of beta particles can be found by the formula C1- C2.
6 Repeat steps 2-5 to obtain 6 sets of readings by varying the distance d .
7. Plot a graph of lg C against lg d. If the graph is linear , the relationship C=kdn is valid. where lg k is the intercept and gradient is n.

Reliability : Use the same source , ensuring that it has a long half life.
Repeat the expt to get average reading.

Safety measures:
1. Handle the source with tongs
2. Do not point the source at anyone.
3. Keep the source in lead box after use.