Alt to prac Flashcards
10 light precautions
- carry experiment out in dark room
- set square to make sure screen is vertical
- measure distance between lens/object by drawing a vertical line from the middle of the lens holder and measure dinstance from there
- move lens back/forth until focused image
- center of lens, object and screen must have same height
- lens, object and screen must be perpendicular to bench
- clamp rule/place on bench
- place pins as far away from each other as possible
- view pins with one eye
- view pins from their basses in case one is not vertical
6 precautions of inaccuracy when measuring angles of relection
- thickness of lines
- thickness of pins/pin holes
- protractor gives reading nearest to one degree
- base of pins might be tilted
- positions of pins might not be exact as ray
- thickness of mirror
4 precautions of taking readings from thermometer for rate of cooling
- insulate beaker to reduce amount of heat loss
- repeat and take average
- stir to ensure water temp is same throughout whole beaker
- use lid to reduce amount of heat loss
3 precautions from reading voltmeter/ammeter
- repeat experiment several times and take average
- check for zero error
- avoid parallax error by looking perpendicular to scale
4 precautions when measuring distances in pivot experiment with masses
- rule is unlikely to balance
- rule could slide on pivot
- mass could slide on rule
- rule isnt uniform so centre of mass of rule is not on the 50cm mark
6 OBSERVATIONS How to make have fair comparison between springs of different material
- same diameter
- same thickness of psring
- same range of loads
- same length of wire
- same number of coils
- same coil spacing
2PRECAUTIONS for spring experiment
- look perpendicular to scale of ruler while taking readings
- wait until spring stops vibrating before vibrating
1 PRECAUTION of thermal experiment
- look perpendicular to the scale of thermometer while taking reading to avoid parallax error
5 CONTROLLED VARIABLES of thermal experiment
- room temp
- initial temp
- volume of liquid
- same beaker and thermometer
- air current
INACCURACY in thermal experiment
heat lost to surroundings
3 WAYS how to overcome INACCURACY in thermal experiments?
- insulate container
- lid
- initial temp is approximately equal to room temp
5 CONTROLLED VARIABLES pendulum experiment
- same stopwatch
- bob released from same height
- same number of swings
- same shape of bob
- same size of bob
4 PRECAUTIONS of pendulum experiment
- no air current in place
- time number of swings/time
- repeat and average
- view perpendicular to rule while measuring height
5 INACCURACIES displacement method
- parallax error
- student didn’t look from meniscus of liquid
- splashes when immerging rock
- air bubbles in rock
- string is too thick
5 PRECAUTIONS displacement method
– shake rock
- thin string
- view perpendicular to scale of cylinder
- look from meniscus
- put rock in gently
4 GENERAL SAFETY PRECAUTIONS
- live wires should not be touched
- gloves for hot objects
- circuit connections are checked
- when changing components of a circuit, power should be switched off so no one will experience electric shock
3 PRECAUTIONS measuring length
- rule parallel to spring
- view perpendicular to reading
- use square
6 PRECAUTIONS optical experiment
- dark room
- object/lens are at the same height
- mark on lens holder to show position of lens center
- take more readings
- repeat and average
- perpendicular while taking readings
3 INACCURACIES electricity experiment
- heating effect of current
- battery used up
- bad connection of sliding contact
2 PRECAUTIONS overcome heat in electricity experiment
- battery of lower emf
- switch off/on between readings
PRECAUTIONS in general for electricity experiments
- view perpendicular while taking readings
- tap on voltmeter/ammeter to check pointer is free to move
- take several readings and average
2 variables are directly proportional if…
- straight line with positive gradient
- line passes through origin
- ratio is constant
how to compare between 2 results to know experimental limit
- divide greater number by smaller one
- multiply DECIMAL of the result by 100 to the percentage error
if below 10% = results are equal within experimental accuracy
if above 10% = results are not equal within experimental accuracy