Alternative to Practical Flashcards
Three points that make a graph directly proportional?
Through origin
Increase at same rate
Positive gradient
Control variables when testing a cooling bulb?
Same starting temperature
Same surrounding temperature
Setting up an optics experiment
Bulb, lens, dark screen 2cm from lens, metre rule between them all
Controls in optics experiments
Dark room
Move lens backwards and forwards to get optimum sharpness
Obtaining accurate readings
Check for zero errors
Repetitions
Proper way to say close enough
Within limits of experimental accuracy
Reasons for errors in measuring angle of incidence/reflection
Thickness of lines
View base of pins
Protractor only accurate to +/- 1 degree
How to be accurate with plumb line
Viewing line directly in front of card
How you can see that a lamps filament is heating up
Brightness changes
Accurate thermometer work
Wait for temperature to stabilise
View thermometer at right angles
Thing for measuring distances
Trundle wheel
Minimum distance for sound experiment
200m
Why only do speed of sound to 2 sig fig?
Time measurements too inaccurate
3 things to do with reflection experiments
Avoid parallax errors when taking readings with protractor
Thin lines
Pins as far apart as possible
How to avoid parallax error when using metre rule?
View scale perpendicularly
Practical difficulty and solution in balancing a metre rule
Ruler never quite balances
Place the ruler where it nearly balances
Centre of mass is not in middle of rule, so does not balance. But the ruler does balance at another point . What does the student do?
Take measurements from point where metre rule balances
Explain briefly how you would reduce the uncertainty in the position of Q required for exact balance
estimate between two best positions that almost balance but tip opposite sides
Controls in lens experiment where you do not have to make sure image is one hundred percent focused
use of darkened room / brighter lamp / no other light interfering
mark position of centre of lens on holder
place metre rule on bench (or clamp in position)
ensure object and lens are same height from the bench
lens / object / screen perpendicular to bench
repeats
avoidance of parallax with action and reason
Range of values for which an image will be focused
+/- 0.5cm
3 things to keep the same when doing the heating rod experiment
• length of rod
• diameter/thickness/area (of cross-section) of rod
• amount of wax / type of wax
• weight / size/mass of marker
• position for the markers
• (Bunsen) flame / (rate of) heating
• position of Bunsen / flame
• position of rod on tripod
Why not to use liquid in glass thermometer
Temperatures too high
Bulb can’t make proper contact
When resistance of variable resistor decreases the lamp gets….
Brighter
Why record 20 swings not 1?
Reduces the effect of error due to stopping/starting stopwatch
