Checklist for Physics Practical

Use ‘/’ to separate the heading label and its unit if the label has a unit eg V/cm.  Exception could be V/(cms^-1). 

If a table is not provided, you have to draw the table in PENCIL (not ink!) and ruler.

The data collected has to be arranged in ascending or descending order. 

Range of data to cover entire quantities given eg 10, 20, 30, 40, 50  if a thread of 50cm is given.  Another eg 5, 10, 20, 30, 40, 45 if a thread of 45cm is given.

Degree of accuracy in any vertical column has to be consistent, i.e if you record the metre rule reading up to 3 decimal place, all data in that column have to be recorded up to 3 decimal place (including zero). The magnitude is usually based on the precision of the instrument used unless otherwise stated.

Data recorded should reflect the sensitivity of the measuring instruments used. For example,
(a) Metre rule ===> to the nearest mm, e.g. 0.500 m, 40.0 cm, etc
(b) Thermometer ===> to one decimal place, e.g. 35.5 °C, 60.0 °C, 76.0 °C 
(c) Stopwatch ===> to the nearest hundredth of a second, e.g. 34.34 s, 0.63 s, 7.00 s
(d) Voltmeter readings ===> to two decimal places, e.g. 2.00 V, 0.65 V (Note: can only estimate for 0.05V)
(e) Ammeter readings ===> to two decimal places, e.g. 0.20 A, 0.34 A

However, if the the degree of accuracy is stated, follow the instructions eg 34.34 s as shown on the stopwatch should be reflected as 34.3 s if instruction is given to be 1 decimal place. 

All data have to be recorded in decimal, not fraction.

Vertical column tabulation is preferred most of the time.

Use mechanical pencils. Do not use 'zigzag' symbol along the axis.

Do not indicate y and x as in mathematics as they are unknowns.

E.g., t/s or M/kg

Use a sensible scale. Select the scale such that the graph covers 75% of the graph paper.

Your graph must be at least ¾ of the graph paper both length-wise and breadth-wise.

This will also depends on whether the origin is required to be plotted.

Mark every big square (2 cm).  If the scales are given in the question, you must use them. You may NOT want to include the origin unless the question asks for it specifically.

The scales for the axes should be based on sensible ratios, e.g. 2 cm on the graph paper representing 1, 2, 5 or 10 units of the variable (or 10, 20, 50 or 100 etc.). Never use odd scales eg 2 cm representing 3, 6, 7 units.

As a general guide, the origin (?, 0) for the vertical axis has to be included if the y-intercept is required.  Similarly, the origin (0, ?) for the horizontal axis has to be included if the x-intercept is required. 

If you are verifying a straight-line relationship, have at least 5-6 points. To plot a curve requires more points(7 points and above).  Take more neighbouring points for plotting of turning points ie maximum or minimum curve.

Plot points carefully, use a cross ‘x’ instead of '." as the "." might be drawn to thick.

If you recorded 5 sets of data, then there should be 5 points on the graph.

The line should be as close to all the points as possible and there should be an equal number of points above and below the line/curve. Do not force a straight line through points which show an obvious curved trend.

The line should be thin and very neat – no hairs or kinks. A graph should be drawn with a mechanical pencil.  Your line must be extended beyond the first and last point on the graph.

Note: Use a 30.0 cm transparent ruler for straight line and a curve/flexible rule for curves.

If a point is obviously off the best-fit line/curve, it can be ignored. Circle the anomalous point on the graph and label it as "ignored".

The size of the gradient triangle must be at least 5cm by 5cm.

The lines should be dotted so as not to confuse with the actual line/curve.

Only points lying on the line of best fit can be used to calculate the line gradient. The two points must be as far apart as possible. Choose points that can be accurately read and not estimated.  Calculation of the gradient should be to three significant figures.

Coordinates must be written beside the points you selected to calculate the line gradient. Choose points that can be accurately read and not estimated.

Note: (x , y) ---- (horizontal , vertical)

Evidence on how a reading is obtained from a graph must be shown clearly with dotted reference lines.

Website

Accuracy and Precision

       Websites (Videos)

1. Vernier Calipers and Micrometer
2. Period of Pendulum
3. Density
4. Principle of Moments
5. Centre of Gravity of an Irregular Object

      Websites(Videos)

1. Reflection of Light
2. Refraction of Light
3. Refraction through Prism
4. Real and Apparent Depth
5. Converging Lens

      Websites (videos)

1. Voltmeter
2. Ammeter
3. Resistance (Series and Parallel)
4. Ohm's Law
5. Variable resistor
6. Wiring of 3 pin Plug
7. Bar Magnet(Plotting compass)
8. Electromagnet
9. DC Motor

If you are not able to start to get a set of decent result, you may seek help from the subject supervisor.  However, marks will be deducted.  You are to read your instructions carefully as important steps may have been neglected.

In general, do not mention the followings as precautions:

1. Switch off fan - Fans are off during exams.

2. Parallax error - This is due to poor experimental techniques.

3. Random errors - Should have already done sufficient sets of results.

4. Heat build up affecting to resistance - Expected to switch off when not measuring.

1) Timing oscillations
(a) Ignored the first few oscillations and start timing only when oscillations are steady.

(b) If the oscillations of the pendulum is elliptical, the timing should be rejected.
(c) Made sure that the angle of swing is small during timing (less than 5°).

1) The water or liquid in the beaker is stirred constantly during the experiment so that the temperature is uniform throughout the water. (Note: Do not use the thermometer as a stirrer)

2) The thermometer is not placed at the bottom of the beaker when the water is heated. This is because the temperature of the beaker is usually higher than that of water. Overheating may lead to over-expansion of the mercury thread thus breaking the thermometer.

3) Temperature readings should be taken only when they are steady.

4) When comparing heat loss due to a change, e.g. the colour of the cooling beaker, make sure that all parameters remain the same except for the colour of the beaker.
(Make sure that starting temperature for both experiments are the same.)

5) When calorimeter is used,
a) it should be covered with a lid to reduce heat loss by convection,

b) it is placed in a shiny jacket lined with good insulating material (e.g. cotton wool) to minimise heat loss by radiation and conduction.

1) Using pins

(a) The 2 pins used to locate the path of a light ray is placed more than 5 cm apart to minimise errors. (Check that pin-pricked points are clearly marked and labelled).  Due to the size of the trace, the pins may not be placed far apart.  This may cause errors in the location of the rays.
(b) View the base of the pins when aligning pins in a straight line as the pins may not be perfectly upright.

(c) The pins are placed vertically upright.

2) Using lenses
(a) Object and image distances should be measured along a line parallel to the principal axis. A set-square is used to minimise parallax errors.
(b) The lens must be upright and parallel to the screen.
(c) The illuminated object should be placed at the same height as the optical centre of the lens.

1) The contacts between the wires and the components and the plug of the switch must be tightened* to reduce contact resistance in the circuit.
(This can be checked by shaking/tapping the connecting wires lightly at each part of the circuit and observe the ammeter's reading. If the reading fluctuates, it means there is a bad connection in the circuit.)

2) Make sure there is no 'kink' in the bare resistance wire especially when you have to measure the length of the wire accurately.  Straighten the wire before measuring.

3) The jockey should be held vertically so that the readings obtained are more precise. Do not exert too much pressure on the resistance wire or slide across the wire, otherwise the cross-sectional area will no longer be uniform.

4) Switch on the circuit for a few seconds before taking a reading and then switch it off immediately. This is to avoid unnecessary heating in the resistance wire as a change in temperature can affect the resistance.

5) The wires are not of uniform thickness thus the reading taken at each point may not reflect teh actual values.

6) To prevent parallax error, use the mirror behind the Ammeter/Voltmeter.  Do not indicate this as the precaution. 

2017: Mechanics (Centre of Gravity -Lamina)

2016: Electricity (Variable Resisitance)

2015: Light (Converging Lens)

2014: Mechanics (Pendulum)

2013: Waves (Transverse)

2012: Light (Refraction - Real and Apparent Depth)

2011: Thermal Energy (Heat Transfer)

2010: Mechanics (Flow rate using Burette) 

2009: Electricty (Variable Resistance)

2008: Moments