2023 CGS Phy Prelims P3 Ans

CRESCENT GIRLS’ SCHOOL SECONDARY FOUR PRELIMINARY EXAMINATION 6091/03 PHYSICS 18 AUGUST 2023 PAPER 3 Practical 1 hour 50 minutes This document consists of 11 printed papers. P R For Examiner’s Use Q1 /10 Q2 /10 Q3 /20 Total /40 Shift Laboratory Class: Register No: Name: ms READ THESE INSTRUCTIONS FIRST Write your name, register number and class in the spaces provided at the top of this page. Give details of the practical shift and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use a 2B pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show working or if you do not use appropriate units. Qualitative Analysis Notes are printed on page 9. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

2 CRESCENT/PRELIM/P3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN Section A 1. In this experiment, you will determine the density of a sphere. You are provided with • five glass spheres, • two half-metre rules, • two set squares, • access to electronic balance. (a) Place the two half-metre rules parallel to one another, with a gap between the two, as shown in Fig. 1.1. Fig. 1.1 (top view) Ensure that the spheres are touching each other and are in a line. Measure the total length L occupied by the 5 spheres. L = 8.0 cm (accept 7.5 to 8.5) (b) Describe, with the aid of a diagram, how you ensured that L was determined as accurately as possible. • Use of set squares at each end of the channels to take scale readings. (accept to grip sphere / hold sphere so that there are no gaps) • One edge of the set square must be aligned with the edge of the ruler. ………………………………………………………………………………………………….. Glass sphere Half metre rule Half metre rule L Set square Glass sphere Half metre rule Half metre rule L

3 CRESCENT/PRELIM/P3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN (c) Use your value of L to determine the average diameter d of a sphere. d = 8.0 / 5 = 1.6 cm d = 1.6 cm (d) Explain why this method of finding average diameter d determined in (c) will give a lower value than the actual diameter d. The set square is placed below the widest point of the sphere (due to the height / thickness of the half metre rule. Hence the value of L measured is lower than actual. (e) Calculate the volume V of a sphere using the equation shown. V = 4𝜋 3 ( 𝑑 2)3 V = 𝟒 𝒙 𝝅 𝟑 ( 𝟏.𝟔 𝟐 )3 = 2.145 = 2.1 cm3 V = 2.1 cm3 (f) Use the electronic balance to determine the mass m of a sphere. m = 5.42 g (accept 5.00 to 6.00) (g) Determine the density of the sphere using the equation shown. ρ = 𝑚 𝑉 ρ = 𝟓.𝟒𝟐 𝟐.𝟏 = 2.6 g / cm3 ρ = 2.6 g / cm3 (h) Suggest a change to the apparatus so that V can be measured directly. Use a measuring cylinder.

4 CRESCENT/PRELIM/P3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 2. In this experiment, you will investigate the power dissipated in a resistance wire. You are provided with • a power supply, • an ammeter, • a voltmeter, • a switch, • a crocodile clip labelled X, • a variable resistor, • a length of resistance wire attached to a metre rule, • leads and crocodile clips. (a) The circuit shown in Fig. 2.1 has been set up for you. (i) Connect the crocodile clip X at the 50.0 cm mark so that the length of resistance wire in the circuit is 50.0 cm. Close the switch. Adjust the variable resistor until the voltmeter reading is 1.00 V. Measure and record potential difference (p.d.) V1 across the resistance wire and the current I1 through the resistance wire. Open the switch. V1 = 1.00 V I1 = 0.14 A (accept 0.12 to 0.16) Fig. 2.1 X

5 CRESCENT/PRELIM/P3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN (ii) Calculate the power P dissipated across the 50.0 cm length of wire using the equation shown. P1 = V1 x I1 P1 = 1.00 x 0.14 = 0.14 = 0.14 W P1 = 0.14 W (b) Do not adjust the variable resistor. Remove the crocodile clip X and connect it so that the length of resistance wire in the circuit is 80.0 cm. (i) Close the switch. Measure and record the potential difference (p.d.) V2 across the wire and the current I2 through the wire. V2 = 1.20 V I2 = 0.11 A (ii) Calculate the power P2 dissipated across the 80.0 cm length of wire. P1 = 1.20 x 0.11 = 0.224 = 0.13 W P2 = 0.13 W

6 CRESCENT/PRELIM/P3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN (a) A student claims that P = GL. where G is a constant and L is the length of the resistance wire in the circuit. Plan an experiment to find out if the student’s claim is correct. In your plan, you should: • identify one other key variable, • describe how you would perform the experiment, • sketch the graph that you would obtain using preliminary observations, • how G can be obtained from your graph, • explain one precaution that you should take to ensure the accuracy of the experiment. 1. Resistance of the variable resistance should remain constant. 2. Setup the experiment as shown in Fig. 2.1. 3. Connect the crocodile clip at the 50 cm mark on the resistance wire. 4. Measure and record the current flowing (through the resistance wire) using the ammeter. Measure and record the potential difference (across the resistance wire) using the voltmeter. Open the switch so that the circuit does not heat up. Calculate the power using P = IV. 5. Repeat step 3 and 4 by connecting the crocodile clip at different positions on the resistance wire. Take a total of 5 sets of readings. 6. Plot a graph of P against L (DV against IV) 7. Graph drawn is straight line linked to P1 and P2. 8. Constant G can be obtained by finding the gradient of the graph. 9. Open the switch when not taking reading to ensure that the wire does not heat up. P/ W L / cm P/ W L / cm

7 CRESCENT/PRELIM/P3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN Section B 3. In this experiment, you will determine the focal length of a thin converging lens. You have been provided with • a converging lens, • a lens holder, • cross wire object, • a light source mounted on a stand, • a screen, • a metre rule, • an A4 piece of card. (a) Describe how you could estimate the focal length of a converging lens using just a lens and a screen.