Tips 4 P6 Exams. Hany El_Gezawy. By Hany El-Gezawy EXAMINER TIPS FOR PHYSICS

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1 Tips 4 P6 Exams By Hany El-Gezawy EXAMINER TIPS FOR PHYSICS 2012/2013

2 Tips 4 P6 Exams 2012/2013 Graphs When plotting a graph it is important to 1. Label axis (y/ unit against x/unit). 2. Choose a proper scale. 3. Choose the scales so that the plots occupy more than half of the graph grid. 4. Students must not use an awkward scale to achieve the size. 5. Plotting should be neat and as accurate as possiblee 6. Graph lines should be neat, thin and a good fit (if there is scatter of points they should lie either side of the line {in a rough way!! }). 7. Straight lines should FILL the page (even beyond the range of points) so that any gradient calculation can use the largest Δy and Δx. 8. Careless, rushed graph plotting can lose several marks. 9. You should always use a sharp pencil and plot small, neat, accurately placed crosses. 10. Draw a Well-judged neat thin best-fit line(s). 11. students should describe what information is obtained from a graph Notes: I. You should understand that if y is directly proportional to x then the graph willl be a straight line through the origin. II. Representing data in a graph, why? A graph is the best way to display the results of an experiment. III. Column headings in tables of readings must be headed with the quantity and unit as in these examples: I/A, orr t/s, or y/m. IV. Graph axes are labeled in the same way. V. Final answers in calculations should be given to 2 or 3 significant figures. Measuring the gradient: a. Draw a triangle on graph b. Use clear lines c. Triangle must be larger than half the line d. Try to use the largest Δy and Δx possible too obtain more accurate value of G. e. G = slope = Δy / Δx To produce more accurate or reliable results: 1. Repeat experiment, to calculate average reading. 2. Avoiding parallax error, look perpendicular to the ruler. 3. If accuracy in measurement was asked, check for zero error. *If values have difference by 0.1 or 0.01, that is the limit off experimental accuracy, so answers are about the same. Hany El Geza wy Page 1

3 Tips 4 P6 Exams 2012/2013 Experiment control Good procedures: - repeat readings to spot anomalous errors or to calculate an average avoid making parallax errors, {the line of sight should be perpendicular to the reading on the scale} look carefully at any scale that is used eg o notice the unit in which the scale is calibrated - always give the unit of any measurement o notice the maximum reading that can be obtained o notice the smallest change in value that can be obtained o aim to use quantities that have magnitudes that are towards the upper values of the scale In experiments involving the measurement of a length When measuring heights ensure that the rule is held perpendicular to the base Know how to arrange apparatus so that it is parallel or perpendicular to a bench Know how to arrange a set square either side of a cylinder/sphere to measure diameter Micrometer : can measure the thickness of any small thing to 0.01 mm Vernier : can measure the inner and outer wall of anything to 1.05mm Time When measuring an interval of time A stopwatch can measure to about 0.1 s, although it may give a reading to 0.01 s For oscillations (of a pendulum or vibrating rule), be able to define a complete oscillation Time N oscillations, usually N>10 and use the terminology periodic time T = t/n Periodic time (T) is measured by timing a number (n) of oscillations, then divide the time taken for all the oscillations by the number of oscillations (n) Explain how to use any aid at the center of the oscillation Explain where the eye should be placed to avoid parallax errors Light Good procedures In light experiments using objects, lenses and a screen Ensure that each item is aligned so that the center of each item is at the same height and on the same horizontal straight line (ideally use the term optic axis) Use a fiducial aid when measuring a length, eg mark the middle of the lens on the bench Try to use a translucent screen Perform the experiment in a shaded part (darkened) of the laboratory In ray tracing experiments When using marker pins space the pins so that they are at least 60 mm apart Ensure that the pins are vertical (or at least their bases are aligned) Draw neat thin lines Hany El Gezawy Page 2

4 Tips 4 P6 Exams 2012/2013 For images produced from lenses on screens, precautions taken: Use of a darkened room for the experiment. Avoiding parallax error in measurement, and look perpendicular to the ruler. Object and lens at the same height from bench. Object/lens/screen is perpendicular to the bench. To draw an image created from lens: a. Inverted from the original object. b. Sides are multiplied by the magnification. Images m =2 m =0.5 Precautions taken in experiments about formation of images by a lens a. Use a darkened area b. Meter ruler on bench or clamped c. Object and lens same height on bench d. Mark on lens holder to show center of lens e. Take more readings f. Avoid parallax error, explain action and reason g. Lens\screen perpendicular to bench Thermal Good procedures When using a thermometer Position the eye so that the mercury thread appears to touch the scale Check whether the thermometer is full or 1/3 immersion In heat experiments Choose volume/mass values of the quantities that give large changes in the temperature Insulate the container, cover the container Stir and wait for highest temperature after stopping heating Improvements that could be done to the experiment (temp. cooling): a. Same initial temperature. b. Same volume of water. c. Same shape of beaker. d. Beakers of same surface. e. Same room temperature. f. Stirring the water in the beakers. Hany El Gezawy Page 3

5 Tips 4 P6 Exams 2012/2013 g. Same time intervals. h. Same surface area. (Unless given different containers) i. Adding water or cooling effect at regular intervals. Accuracy a. Add insulation b. Keep constant room temperature c. Avoid heat loss Heat loss could be reduced by: a. Insulation of beaker (using a calorimeter). b. Covering beaker with a lid. If an experiment were to be repeated in order to determine an average temperature for each time, it would be important to control the conditions. Suggest two such conditions that should be controlled. a. same starting temperature b. constant room temperature/avoid draughts/same place c. same time intervals d. same thermometer e. same mass/amount/volume of water f. same beaker g. lid always used Electricity You need to know that to read the current through a component (e.g. a lamp or a resistor) and the voltage across it, The ammeter is placed in series with the component but The voltmeter must be connected in parallel with the component. It is important to be able to set up a circuit from a diagram, draw a circuit diagram of a circuit already set up and also to draw a circuit diagram from a written description. In electrical experiments Check for a zero error Always check that connections are clean. Switch off the current when not making a measurement. When measuring resistance use low currents/voltages to avoid heating and changing the resistance you are measuring Physics laboratory safety precautions / rules: 1. Live wires should not be touched. 2. Hot Objects should not be touched with barren hands instead of that gloves should be used the most common process is heating of water in thermodynamic experiments. 3. Circuit connections should be checked and approved by the teacher and then only the circuit should be switched ON. Hany El Gezawy Page 4

Tips 4 P6 Exams 2012/2013 4. While changing components of the circuit the power should be switched so that one should not experience electric shocks. 5.

6 Tips 4 P6 Exams 2012/ While changing components of the circuit the power should be switched so that one should not experience electric shocks. 5. Safety spectacles, gloves and other safety components should be used while handling experiments. 6. While handling a mercury thermometer one should take of the mercury spills. 7. No other laboratory instruments should be touched or handledd which is not involved in the course of experiments. Stretch Hooke s Law For spring extension experiment, variables that should be constant in the experiment: a. Number of coils. b. Diameter of spring. c. Selection of loads. d. Mass of spring. micrometer : can measure the thickness of any small thingg to 0.01 mmm vernier : can measuree the inner and outer wall of anythingg to 1.05mm How to check if a rule is vertical: a. Protractor b. Use of set square c. Plumb line d. Spirit Level Variables in experiments about springs and stretching effect: a. Number of coils b. Length of spring c. Diameter\thickness of spring or wire d. Range of loads e. Length of wire f. Coil spring Sources of error in calculating circumference by string method: a. Parallax b. Diagonal winding c. Thickness of string Improvement made to calculating circumference by stringg method a. Avoid parallax error b. Repeats and average c. Thinner string d. Parallel winding of springs Students should understand the idea of a fair test or comparison in which only one variable is altered at a time, eg when investigating how rate of coolingg experiment depends on temperature room to be kept constant--room draughts, volume and type of liquid, amount of stirring. Students should be trained to give a conclusion to an experiment. Hany El-Gezawy Hany El Geza wy Page 5

Physics (Alternative to Practical) 62 Tuesday

Physics (Alternative to Practical) 62 Tuesday Just study all 5 Topics of physics: General Physics Thermal Physics Waves Magnetism Atomic Physics 1 And you'll do fine For paper 6 learn all the 5 topics