PHYSICS
PAPER 3
FORM 4 MID TERM 2
INSTRUCTIONS
 You are advised to spend the first 15 minutes of the hours given reading the entire question paper
 Answer all the questions in the spaces provided
 Marks are given for clear record of observations actually made for their suitability and accuracy for the use of them.
 Candidates are advised to record their observations as soon as they are made.
 K.N.E.C Mathematical tables and Non programmable silent electronic calculators may be used.
 QUESTION ONE
 PART A
You are provided with the following apparatus: A screen with cross wire
 lens and a lens holder
 A white screen
 About 10cm candle stick
 A Metre rule
 Lighting source.(match box)
Proceed as follows: Arrange the lens and screen as shown in the diagram below.
Adjust the distance of the lens from the screen until a sharp image of a distant object is formed on the screen. Measure and record the distanced cm (1mk)
d = ..............................................cm  Place the metre rule on a horizontal table so that the millimeter scale faces upwards, place the candle at one end of the metre rule and the screen with cross wire at the zero cm mark (just near the candle).Arrange the lens and the white screen as shown below:
 Adjust the lens so that the distance x is 30cm.
 Adjust also the position of the white screen to obtain a sharp image of the cross wire and record the value of y in the table below.
 Repeat steps b (i) and b (ii) above for values of x = 35cm, 40cm,45cm,50cm and record the corresponding values of y each time in the table below.
 Hence complete the table. (4mks)
x(cm) 30 35 40 45 50 y(cm) y + x (cm) yx (cm^{2})
 Plot a graph of (y + x) ( y  axis) against yx. (xaxis) (4mks)
 Determine the gradient of your graph. (2mks)
 Given that the equation of graph is 1=F(^{y+x}/_{xy})
Use the graph to find the value of (f) (2mks)
 Arrange the lens and screen as shown in the diagram below.
 PART B
You are provided with the following: A boiling tube
 Some dry sand
 A liquid in a measuring cylinder labelled L
 Half – metre rule
 A vernier calipers (to be shared)
 A weighing machine (one per room)
 Tissue paper
Proceed as follows:
 Measure the length of the boiling tube
h = ...........................................................................cm (1 mk)  Put a little amount of sand in the boiling tube and place it in the measuring cylinder which is almost filled with a liquid labelled L. Add sand, little by little until the tube floats upright as shown in figure 2.
Measure the length, d, of the boiling tube which is above the liquid
d = .........................................................................cm (1mk)  Determine the length, t, of the boiling tube which is immersed in the liquid
t = ...........................................................................cm (1/2 mk)  Remove the boiling tube from the measuring cylinder; wipe it dry (on the outside) and weigh its mass, m, including the sand inside.
m = .........................................................................g (1mk)  Measure the external diameter, D, of the boiling tube
d = ..........................................................................cm (1 mk)  Determine external radius, R,
R = .........................................................................cm (1⁄2 mk)  Using the formula
m = ρ x (πR^{2}), determine ρ for the liquid
ρ= .......................................................................... (2mks)
 Measure the length of the boiling tube

 PART A
 QUESTION TWO

You are provided with the following Ammeter
 Voltmeter
 A jockey
 2 dry cells
 A mounted nichrome wire
 6 connecting wires
 A cell holder
 Connect your apparatus as shown in the circuit diagram below
 Adjust the length MP of the resistance nichrome wire to be 75cm from M to P and record the ammeter and voltmeter readings in the table below.
 Reduce the length of MP by 15cm such that the new length of MP is now 60cm. Record the ammeter and voltmeter readings.
 Repeat the procedure above when the length of the wire MP = 45cm, 30cm, 15cm and 0cm from M and record the readings in the table below.
Length L(cm) 75 60 45 30 15 0 p.d(V) Current I(A)  Plot a graph of p.d (V) against current I (5mks)
 Determine the slope of the graph (3mks)
 Find the internal resistance r of the battery from the graph given that V = E – Ir (2mks)
 Determine the e.m.f E from the graph (1mk)
 Connect your apparatus as shown in the circuit diagram below
 Connect your circuit as shown in the diagram below
 When the jockey is at the furthest end of the resistance wire at Q. Find the ammeter and voltmeter readings
V___________V (1mk)
I___________A (1mk)  Calculate the resistance of the nichrome wire (3mks)
 When the jockey is at the furthest end of the resistance wire at Q. Find the ammeter and voltmeter readings

MARKING SCHEME
 QUESTION ONE
 PART A
 d = 20 ± 2cm 1mks

 Table
x(cm) 30 35 40 45 50 y(cm) 60 47 40 36 33 y + x (cm) 90 82 80 81 83 yx (cm^{2}) 1800 1645 1600 1620 1650
y + x 4 – 5 correct = 1mks
3 correct = 1/2mk
yx 4 – 5 correct = 1mks 3 correct = 1/2mk
 Table

Simple and uniform scale = 1mk
Plotting 4 – 5 points = 3mks
Straight line through 4 5 points = 1mks  Slope/gradient
slope = 88 – 80 intervals correctly substituted = 1mk
1760 – 1600
= ^{8}/_{1600} Correct evaluation and
= 0.05/cm Accuracy + unit = 1mk  f – value
Equation of graph
y + x = ^{1}/_{f} xy correct equation and equating slope to ^{1}/_{f} = 1mk
slope = 0.05/cm =^{ 1}/_{f}
slope = ^{1}/_{f} correct evaluation
f = 1/slope = 1/0.05 = 20cm = accuracy + unit = 1mk
= 20cm ± 2
 Part B

 h = 14.5 ± 1cm ( 1mk)
 d = 4.0cm ± 1cm ( 1mk)
 t = h – d = 14.5 – 4.0 = 10.5cm ( 1⁄2 mk)
 m = 45g (1 mk) candidates value within range of 35 – 55g
 D = 2.45cm ± 0.1cm (1 mk)
 R = D/2 = 2.45/2 = 1.225cm follow candidates work ( 1⁄2 mk)
 45 = ρ x 3.142 x (1.225)^{2} 1mk
ρ = ^{45}/_{4.715 }= 9.54g/cm^{3}

 PART A


Length (cm) 75 60 45 30 15 0 p.d(V) 2.7 2.6 2.5 2.38 1.9 1.1 Current I (A) 0.9 1.1 1.3 1.60 2.45 2.5  Slope = 2.65 – 2.25;
1 – 1.8
= ^{0.4}/_{ 0.8 }=  0.5 ;  V = E – Ir
V =  Ir + E;
R = 0.5Ω;  V– intercept 3.1V ;
 Slope = 2.65 – 2.25;

 V = 2.4V
I = 0.8A  r=^{v}/_{I}= ^{2.4V}/_{0.8A }=3Ω
 V = 2.4V

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