2022/23 CHS Physics Practical Notes

1 Name: ( ) Class: 3 - Catholic High School 2022 Level 3 Physics Practical NOTES No. Contents Pg I Singapore-Cambridge General Certificate of Education Ordinary Level (2018) (Syllabus 6091 - Physics) 1 II Introduction to Physics Practical Experiments 6 III Physics Practical Experiment Skills 7 IV Physics Practical Experiment Notes 8 V Physics Sample Graph Plotting 23

2 (I) Singapore-Cambridge General Certificate of Education Ordinary Level (2018) (Syllabus 6091 - Physics)

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7 (II) Introduction to Physics Practical Experiments Basic safety procedures It may appear to some people that doing Physics practical experiments is less dangerous than doing Chemistry or Biology experiments. This is a serious misconception. Doing any experiment in the laboratory can be dangerous if we do not follow some basic safety procedures. Below are some basic safety procedures that we should be aware of. Before you begin 1. Make sure that your workbench is not full of unnecessary things (such as school bags, files, clothes and books). 2. Read all the instructions and check that the apparatus provided on the table match those in your worksheets before you do anything. 3. Look out for any possible dangerous procedures. While you are doing the experiment 1. Follow the directions in the worksheet closely. Do not do anything you are not instructed to do without your teacher’s permission. 2. Do not fool around and endanger yourself or the people around you. 3. Wear or use protective devices that are provided for you. These include goggles, gloves and safety tongs. 4. Never leave heating apparatus unattended. Turn off Bunsen burners and gas when you have to leave your workbench for a while or when you have finished your experiments. 5. If you have broken any glassware (eg. beakers, test tubes and thermometers) or spilt anything, inform your teacher immediately. You may have to help in cleaning up. 6. Be aware of where the fire extinguishers are located in the laboratory. After you have finished the experiment 1. Clean up your workbench. 2. Do not dispose of materials in the sink unless you are instructed to do so. 3. Wash your hands thoroughly. The above are only some of the safety procedures that you should take to avoid accidents. It is not possible to list all the safety procedures. The best preventive measure to take is to always be careful and be alert. Take care of yourself and your neighbours.

8 (III) Physics Practical Experiment Skills For practical experiments, always bring 1. A blue or black pen 2. A sharpened pencil (with sharpener) or mechanical pencil (with spare pencil lead) 3. A 30.0 cm clear plastic ruler (do not assume that the lab will provide a ruler) 4. Flexible curve 5. Calculator 6. Eraser During practical experiments, you will develop the following experimental skills: 1. 2. Carry out techniques, use apparatus, and handle measuring devices and materials effectively and safely based on instructions. 3. Make and record observations, measurements and estimates with due regard to precision, accuracy and units. 4. Interpret, evaluate and report observations and experimental data. 5. Evaluate methods and suggest possible improvements. 6. Plan an experiment by identifying key variables, outlin ing experimental procedures with appropriate instruments, explaining how to process the data and identify ing any risks and associated precautions to minimise them. Display of data 1. Take at least 5 sets of readings for straight lines (or at least 7 sets of readings for curves). 2. Plan all your readings so that they are uniformly spread out within the given limits. 3. All raw data under the same column must be recorded to the same number of decimal places (based on the precision of the measuring instrument). 4. When determining the average value of a set of raw data, , it should be recorded to the same precision (i.e. same number of decimal places) as the raw data taken. E.g.: Average of 2.36, 2.41 and 2.38 = (2.36 + 2.41 + 2.38) ÷ 3 = 2.383 = 2.38 (2 d.p.) Precision of readings (for information only) Instruments Precision Metre rule 0.1 cm Vernier Calipers 0.01 cm Micrometer Screw Gauge 0.01 mm Measuring Cylinder (100 cm3) 0.5 cm3 Protractor 1° Digital Stopwatch 0.1 s Thermometer 0.5 °C (or 1 °C, depending on instrument used) Spring Balance 0.05 N Digital Balance 0.1 g (or 0.01 g, depending on instrument used) Standard Masses 1 g Ammeter (0 - 1A) 0.01 A Milliammeter (0 - 100 mA) 1 mA Voltmeter (0 - 3 V) 0.05 V Resistor 1 Ω Electronic Balance 0.1 g or 0.01 g (depending on instrument)

9 (IV) Physics Practical Experiment Notes Physics practical experiments are concerned with measurements. Measurements are only useful if they are correctly taken, recorded, processed and analysed. Do take note of the following points when taking measurements: 1. Parallax error An important skill in Physics p ractical experiments is reading a scale correctly. Parallax error which arises from the incorrect positioning of the eye results in incorrect scale readings. To avoid such an error, the following precautions should be kept in mind when using the various instruments: (a) Metre rule The eye must always be placed vertically above the point X (the reading to be taken) on the scale. Thermometer (c) Ammeter Move your head above the ammeter until the pointer covers its image in the mirror . (d) Measuring cylinder For liquids other than mercury, read off the meniscus at eye level as shown.

10 2. Use of measuring instruments (a) Metre rule Metre rules are graduated in millimetres (mm). Readings taken with a metre rule are recorded in centimetres to one decimal place, e.g. 20.5 cm or 40.2 cm. (b) Vernier calipers Vernier calipers are used to measure lengths in centimetres precise to two decimal places, i.e. 0.01 cm. Refer to Chapter 1 notes to learn how to read vernier calipers. (c) Micrometer screw gauge The micrometer screw gauge is an instrument for measuring the diameters of wires and thin rods in millimetres precise to two decimal places, i.e. 0.01 mm. Refer to Chapter 1 notes to learn how to read micrometer screw gauge. 3. Precision of readings To quote say 34.12 °C for the temperature of a sample of liquid, you are actually telling others that in your measurement, you are certain of all the digits but the last. This precision cannot be obtained with the ordinary thermometer used in the school laboratory. Never quote more decimal places for the readings or final answer than what the instrument can provide. 4. Addition and subtraction When two or more values are added or subtracted, the result will have the same number of decimal places (d.p.) as the given values. E.g.: 21.22 cm + 12.66 cm = 33.88 cm (2 d.p.) [For information only : At A -level Physics, when adding or subtracting two or more values, the number of decimal places of the result will follow the given value which has the least number of decimal places (d.p.) . However, such calculations (involving values with different d.p.) never occur at O-level Physics.] 5. Significant figures To determine the number of significant figures in a number, apply the following rules: 1. The following figures in a number are significant: (a) All non-zero figures. E.g.: 7.12 has 3 significant figures. (b) All zeros between non-zero digits. E.g.: 2003 has 4 significant figures. (c) All zeros after a non-zero digit in a decimal. E.g.: 22.300 has 5 significant figures.