Note : Some of this is not applicable to IGCSE Physics, as it has been submitted by an O-Level Student, but is nonetheless useful.
Calculation
- Addition and Subtraction : same number of decimal places as the number with the least.
- Multiplication and Division : same number of sf as the number with the least.
Graphs
- Draw and label the axis’
- Give the graph a title
- Ensure that the scale is clearly marked out
- Ensure that the graph covers more than 50% of the paper.
y
x
- Y is directly proportional to x
y
x
- Y is linearly related to x
y
x
- Y is linearly related to x with a negative gradient
y
x
- When x is increased, y increases at a decreasing rate
y
x
- When x is increased, y decreases at a decreasing rate
y
x
- When x is increased, y increases at an increasing rate
y
x
- When x is increased, y decreases at an increasing rate
When asked for gradient : magnitude and unit
When asked for constant g : only the magnitude
——————————————————————————
Reason for taking multiple readings when using a stopwatch :
It is to reduce the random error and increase the accuracy of the results by finding the average.
Improving the accuracy of pendulum results :
- Increase the number of timed oscillations and then find the average.
- Mark the centre on the pendulum bob in order to measure accurately.
Lenses experiments sources of error :
- There exists a small range of distances for which the image is still in focus which may lead to an uncertainty in the measurement of the focal length.
Improvement : take more readings and then find the average
Sources of error for experiments with thermal energy :
- Some of the thermal energy is given out to the surroundings and is not accounted for.
- The source of heat heats up the instrument along with the material intended to be heated too.
- Thermal energy is lost through the evaporation of water.
Improvements :
- Include the mass and the specific heat capacity of the beaker/whatever instrument that is not intended to be heated up in the calculation as that instrument is being heated up and is absorbing thermal energy too.
- Cover the beaker with a lid and place the thermometer through the lid. This is to reduce thermal energy loss by the evaporation of water.
- Place the styrofoam cup in a beaker to provide thermal insulation and prevent the loss of thermal energy.
——————————————————————————
Planning Questions
- State the iv, dv and cv (usually 2-3 cv)
- Description of the experiment
- How the iv is varied
- How the dv is varied
- How the data is recorded
Remember to take multiple readings and then find the average !!
- Data processing
- State what graph has to be plotted
- State how to find the variables that the question asked for
——————————————————————————
Improvements for mass related experiments :
- The mass could be taped to the ruler to ensure that the mass does not move during the reading (this increases the accuracy)
- The mass could be replaced with a mass with a clearly defined centre of gravity so that all data needed can be more clearly measured.
Checking that a half metre rule/any rule is horizontal :
Ensure that the rule is horizontal by measuring that the height above the bench at each end and ensuring that they are the same.
Precaution and explanation for experiments with oscillation :
P : Wait for a few seconds before starting the stopwatch and measuring the time for the needed number of oscillations
E : The first few oscillations are unstable and do not have the same period as the remaining oscillations
P : Use an optical pin / blu tack as a fiduciary point when measuring the oscillations
E : To ensure that the 10 oscillations are measured accurately
Technique to obtain an image that is in sharp focus :
Approach the formation of the sharp image on the screen from both directions
Explain why neither f1 nor f2 is equal to the weight of the mass on the string
There is friction between the tube and the rope. Additional force is introduced between the tube and the rope and hence, f1 and f2 are not equal to the weight of the mass on the string.
——————————————————————————If any calculation is obtained by any estimation involved then it is not accurate. Thus, the calculation/value found will be inaccurate.
——————————————————————————
Circuit related :
- The strength of the battery could be varying causing changes in the readings.
- Surrounding temperature increases, resistance decreases (thermistor)
——————————————————————————
When comparing two methods :
The method with lesser quantities to be measured is better because there is a lesser possibility to get inaccurate readings.
Light related :
- Use thinner pins so that the holes made are small and it will not affect the accurate construction of the incident and the emergent rays.
- Separation between the 2 pins along the incident and the refracted rays should be maximised so that the lines joining the pin holes will be a more accurate representation of the rays.
Put a lid on a cup with liquid to decrease the rate of evaporation.
prepIGCSE 