PHYSICS
PAPER 3
PRACTICAL
INSTRUCTIONS TO CANDIDATES
 Write your name and admission number in the spaces provided.
 Answer ALL questions in the spaces provided in the question paper.
 You are supposed to spend the first 15 minutes of the allowed for this paper reading the whole paper carefully before commencing the work.
 Marks are given for a clear record of the observations actually made, their suitability, accuracy and the use made of them.
 Candidates are advised to record their observation as soon as they are made.
 Non programmable silent electronic calculators may be used.
 This paper consists of 8 printed pages.
 Candidates should check the questions to ascertain that all the pages are printed as indicated and that no question are missing.
 Candidates should answer the questions in English.
QUESTION 1 (20 marks)
 You are provided with the following;
 A galvanometer
 A dry cell and a cell holder
 A switch
 A wire labelled Y mounted on a piece of wood.
 Eight connecting wires each with a crocodile clip at one end.
 A resistance wire labelled AB mounted on a millimeter scale.
 Six 10 Ohm carbon resistors
 A jockey or crocodile clip
 Micrometer screw gauge (to be shared)
Proceed as follows: Set up the circuit as shown in figure below, with X being one of the 10 ohms carbon resistors.
 Close the switch. Tap the jockey at various points on the wire AB and locate point P at which the galvanometer shows zero deflection, measure and record in table below the length, where = PB.
 Repeat the procedure in (b) using X as two 10Ω resistors, three resistors, four resistors, five resistors and six resistors. X is the effective resistance for the parallel combination i.e. x = ^{10}/_{n} where n is the number of resistors in parallel.
 Record your readings in table below. (6mks)
TABLE
Number of 10Ω
Carbon resistorOne Two Three Four Five Six X (Ω) L (cm) 1/x (Ω^{1}) 1/L(cm^{1})  Plot a graph of 1/L (yaxis) against 1/x. (5mks)
 Determine the slope m of the graph. (2mks)
 Given that 1/L = R/KX + 1/K where K = 100cm. Use the graph to determine R. (2mks)
 Measure the diameter d and the length of wire Y. (2mks)
=…..……..…………………………..….m
d = ………….…………………………….. m  Determine its crosssectional area A of the wire Y. (1mk)
A =………………………………………… m 2  Determine the resistivity of the wire Y given that its Resistance, R= 1/A(2mks)
 Set up the circuit as shown in figure below, with X being one of the 10 ohms carbon resistors.
QUESTION 2 (20 marks)
PART A
You are provided with the following;
 Meter rule
 Retort stand, clamp and boss
 A spring and with a pointer
 Three masses (a 100 g and two 50g masses)
 Stop watch
Proceed as follows
 Set the apparatus as shown below.
 Hang the unloaded spring and record the pointer readings
x_{o}………………………………………………………….…………………………. m. (1mk) 
 Load a mass of 150 g and determine the extension of the spring, e_{1} .
e_{1}……………………………………………………………………………. m. (1mk)  Displace the 150 g mass slightly downwards and release it to oscillate vertically. Time 20 oscillations and obtain time t_{1} t_{1} ………………………………………………….. (1mk)
 Find periodic time T 1
T_{1} …………………………………………………. (1mk)  Use the equation to find the value of P^{1} . (2mks)
 Load a mass of 150 g and determine the extension of the spring, e_{1} .

 Load a mass of 200 g and determine the extension of the spring, e_{2} .
e_{2}……………………………………………………………………………. m. (1mk)  Displace the 200 g mass slightly downwards and release it to oscillate vertically.
Time 20 oscillations and obtain time t_{2} .
t_{2} ………………………………………………….. (1mk)  Find periodic time T_{1}
T_{1} …………………………………………………. (1mk)  Use the equation to find the value of P_{2} . (2mks)
 Load a mass of 200 g and determine the extension of the spring, e_{2} .
 Find the average of P (2mks)
Pav = P² + P¹
2
PART B
Apparatus Lens and a lens holder
 A candleScreen
 A metre rule.
Procedure
 Focus a distant object and estimate the focal length, f of the lens
f …………………………………………. mm. (1mk)  Set up the apparatus as shown below.
 Set the distance s= 60 cm.
 Adjust the position of the lens to position p where a magnified sharp image is formed on the screen. Record position P.
P =………………………………………. cm. (1mk)  Maintaining distance s, adjust the lens to position P’ where a diminished sharp image is formed on the screen. Record position, P’.
P’ = ……………………………………… cm. (1mk)  Find distance d, between the original position and final position of lens
d = ………………………………………... cm (1mk)
 Adjust the position of the lens to position p where a magnified sharp image is formed on the screen. Record position P.
 Using the formula s^{2}  d^{2} = 4 Find the value of q. (2mks)
 What physical quantity do q represent (1mk)
CONFIDENTIAL
QUESTION 1
Each candidate will require
 Centre zero galvanometer
 One new size D dry cell & cell holder
 A switch
 Eight connecting wires each with crocodile clip at one end.
 A piece of nichrome wire swg 28 (diameter 0.32 mm) of length 30cm.
 Teacher to mount the piece of wire on piece of wood and label it Y see
 A resistance (nichrome wire gauge 30) wire labeled AB 100cm long mounted on a millimeter scale
 Six 10 Ohms carbon resistors.
 A jockey (a crocodile clip may be used)
 A micrometer screw gauge
QUESTION 2
Each candidate will require:
 A spiral spring of spring constant of approximately 10.0N/m.
 A complete stand
 A metre rule.
 Lens (focal length = 10cm) and a lens holder.
 A candle
 Screen
 Three masses (one 100g and two 50g masses)
 A stop watch
MARKING SCHEME
QUESTION 1 (20 marks)
 You are provided with the following;
 A galvanometer
 A dry cell and a cell holder
 A switch
 A wire labelled Y mounted on a piece of wood.
 Eight connecting wires each with a crocodile clip at one end.
 A resistance wire labelled AB mounted on a millimeter scale.
 Six 10 Ohm carbon resistors
 A jockey or crocodile clip
 Micrometer screw gauge (to be shared)
Proceed as follows: Set up the circuit as shown in figure below, with X being one of the 10 ohms carbon resistors.
 Close the switch. Tap the jockey at various points on the wire AB and locate point P at which the galvanometer shows zero deflection, measure and record in table below the length, where = PB.
 Repeat the procedure in (b) using X as two 10Ω resistors, three resistors, four resistors, five resistors and six resistors. X is the effective resistance for the parallel combination i.e. x = ^{10}/_{n }where n is the number of resistors in parallel.
 Record your readings in table below. (6mks)
Number of 10Ω
Carbon resistorOne Two Three Four Five Six X (Ω) 10 5 3.333 2.5 2 1.667 (L cm) 66.5 53.3 48.2 43.5 40.2 37.4 1/x (Ω^{1}) 0.1 0.2 0.3 0.4 0.5 0.6 1/L(cm^{1}) 1.515 1.876 2.075 2.299 2.488 2.674
Plot a graph of 1/L (yaxis) against 1/x. (5mks)  Determine the slope m of the graph. (2mks)
 m = (2.2  2.5) 10‾² cm^{1}
(0.35  0.10)^{ 1}
(Correct substitution = 1mk)
(Correct evaluation with units = 1mk)
Wrong unit = 0mk, no unit = half mark
 m = (2.2  2.5) 10‾² cm^{1}
 Given that where 1/L = r/KX + 1/K where K = 100cm. Use the graph to determine R. (2mks)
 Slope = R/K
(Correct substitution = 1mk)
=28
(Correct evaluation = 1mk)
 Slope = R/K
 Measure the diameter d and the length of wire Y. (2mks)
 I = 30.0/100 = 0.300 m ±0.01 (Value within the range and 3dp a must = 1mk)
d = 0.32/100= 0.0032m ± 0.00002(Value within the range and 5dp a must = 1mk)
 I = 30.0/100 = 0.300 m ±0.01 (Value within the range and 3dp a must = 1mk)
 Determine its crosssectional area A of the wire Y. (1mk)
 (Correct substitution = mk)
A m^{2} (Correct evaluation = mk)
 (Correct substitution = mk)
 Determine the resistivity of the wire Y given that its Resistance, (2mks)
 7.508 x 10^{7}m
(Correct substitution = 1mk)
(Correct evaluation = mk, rule for units applies)
 7.508 x 10^{7}m
QUESTION 2 (20 marks)
PART A
 You are provided with the following;
 Meter rule
 Retort stand, clamp and boss
 A spring and with a pointer
 Three masses (a 100 g and two 50g masses)
 Stop watch
Proceed as follows Set the apparatus as shown below.
 Hang the unloaded spring and record the pointer readings
 x_{o} = student value (3d.p a must) m (1mk)

 Load a mass of 150 g and determine the extension of the spring, e 1 .
 e_{1} = difference in student values = 0.148 ± 0.0 m (1mk)
(Correct subtraction = mk, correct evaluation =mk)
 e_{1} = difference in student values = 0.148 ± 0.0 m (1mk)
 Displace the 150 g mass slightly downwards and release it to oscillate vertically. Time 20 oscillations and obtain time t 1 .
 t 1 = 16.37 ± 0.5 (1mk)
(Value within the range and 2dp a must = 1mk, no unit deny a half mark)
 t 1 = 16.37 ± 0.5 (1mk)
 Find periodic time T 1
 T 1 = ^{16.37}/_{20} = 0.8184s
(Correct division = mk, correct evaluation with unit=mk)
(1mk)
 T 1 = ^{16.37}/_{20} = 0.8184s
 Use the equation to find the value of P 1 . (2mks)
 P =^{ 0.148}/_{0.01616} = 9.158 m/s^{2}
(Correct substitution = 1mk)
(Correct evaluation to 4sf = 1mk)
 P =^{ 0.148}/_{0.01616} = 9.158 m/s^{2}
 Load a mass of 150 g and determine the extension of the spring, e 1 .

 Load a mass of 200 g and determine the extension of the spring, e 2 .
 e2 = x_{2}  x_{0} = 0.196 ± 0.01 m. (Correct subtraction =
mk, correct evaluation=mk). (1mk)
 e2 = x_{2}  x_{0} = 0.196 ± 0.01 m. (Correct subtraction =
 Displace the 200 g mass slightly downwards and release it to oscillate vertically. Time 20 oscillations and obtain time t 2 .
 t _{2 }= 18.62 ± 0.5s (1mk)
(Value within the range and 2dp a must = 1mk, no unit deny a half mark)
 t _{2 }= 18.62 ± 0.5s (1mk)
 Find periodic time T 1
 T_{2} = ^{18.62}/_{20} = 0.9310s
(1mk) (Value within the range and
2dp a must = 1mk, no unit deny a half mark)
 T_{2} = ^{18.62}/_{20} = 0.9310s
 Use the equation to find the value of P_{2} . (2mks)
 (Correct substitution = 1mk)
(Correct evaluation to 4sf = 1mk)
 (Correct substitution = 1mk)
 Load a mass of 200 g and determine the extension of the spring, e 2 .
 Find the average of P
 (Averaging principle = 1mk). (2mks)
(Correct evaluation to 4sf = 1mk)
PART B
Apparatus  Lens and a lens holder.
 A candle
 Screen
 A metre rule.
Procedure
 (Averaging principle = 1mk). (2mks)
 Focus a distant object and estimate the focal length, f of the lens
 f mm ± 10 mm (1mk)
 f mm ± 10 mm (1mk)
 Set up the apparatus as shown below.
 Set the distance s= 60 cm.
 Adjust the position of the lens to position p where a magnified sharp image is formed on the screen. Record position P.
 P = Student’s value (1d.p a must) cm. (1mk)
 P = Student’s value (1d.p a must) cm. (1mk)
 Maintaining distance s, adjust the lens to position P’ where a diminished sharp image is formed on the screen. Record position, P’.
 P’ = Student’s value (1d.p a must) cm. (1mk)
 P’ = Student’s value (1d.p a must) cm. (1mk)
 Find distance d, between the original position and final position of lens
 d = cm (1mk)
(Correct subtraction = mk, correct evaluation =mk)
 d = cm (1mk)
 Adjust the position of the lens to position p where a magnified sharp image is formed on the screen. Record position P.
 Using the formula . Find the value of q. (2mks)
 (Correct substitution = 1mk)
 (Correct evaluation to 4sf = 1mk)
 What physical quantity do q represent (1mk)
 Focal length of the lens used.
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