(6091) Practical Flashcards
what is the no. of decimal places + smallest division of an ammeter?
2 d.p in A + 0.01 A
what is the no. of decimal places + smallest division of an electronic balance?
2/3 in dp in g + follow dp in instrument
what is the no. of decimal places + smallest division of half metre rule or metre rule
no dp in mm/1 dp in cm/3 dp in m + 1mm + 0.01 cm + 0.001 m
what is the no. of decimal places + smallest division of a measuring cylinder?
1 dp in cm^3 + 0.5 cm^3 (half of smallest)
what is the no. of decimal places + smallest division of vernier calipers
2 dp in cm + 0.01 cm
what is the no. of decimal places + smallest division of a micrometer screw gauge?
2 dp in mm + 0.01 mm
what is the no. of decimal places + smallest division of a milliammeter
no d.p in mA + 1mA
what is the no. of decimal places + smallest division of spring balance?
2 dp in N + 0.05N (half of smallest division)
what is the no. of decimal places + smallest division of digital stopwatch?
2 d.p in s / 1 dp in s + 0.01s or 0.1s (corrected due to human reaction time)
what is the no. of decimal places + smallest division of a thermometer?
no d.p in degree Celsius / 1 dp in degree Celsius + 1 degree C/0.5 degree C
what is the no. of decimal places + smallest division of voltmeter?
2 dp in V/ 0.05 V (half of smallest division)
what is the no. of decimal places + smallest division of a protractor?
no d.p in degree / 1 degree
what are precautions in taking readings?
measured readings follow the accuracy of the instrument + calculated readings follow significant figures of measured readings + column of values must be consistent throughout + tables just have headings with units + at least 5 sets of readings
what are things you should not do when taking readings?
give readings in fractions + give units in the tables
what should the range of readings be?
include the minimum and the maximum range possible + be evenly distributed as much as possible
when there is no instruction, how many sets of readings should be taken for a straight-line graph?
minimum 5 sets
when there is no instruction, how many sets of readings should be taken for a curve graph?
8-10 sets
what are the two main things in headings in tables?
the headers (what you are measuring) / unit (the unit of the thing you are measuring)
what is the number of decimal places that addition/subtraction of raw data should be rounded off to?
least number of decimal places of the raw data
what is the number of decimal places that multiplication/division of raw data should be rounded off to?
least number of decimal places for the raw data
how do ratIos/functions get calculated off to?
decimal numbers NO FRACTIONS BTW
what are things to be aware of when plotting the axes of a graph?
follow the question, with the format always going plot a graph of y against x
how much of the paper should a graph have to cover?
3/4 of the paper + plotted points covering a range of 50% vertically and horizontally
what type of scales should be used when plotting out graphs?
1, 2, 4, 5, 10
how big should the plotted points be drawn out as?
1/2 of the smallest square
what is considered a best fit line/curve?
if all the plotted points are close to the line/curve
what are things you must label on ur axis?
y header + x header + origin + scale of y + scale of x
how to find gradient from a graph?
the two points chosen should be as far apart as possible + triangle drawn must be in dotted line + coordinates must written on points used + gradient may have units if you’re finding a known constant
how do you find corresponding x/y values?
draw a line at the corresponding y/x value and vice versa
what should you not do when drawing graphs?
force straight line graph through origin unless stated in question + use zig-zag symbol + use crosses as coordinates of gradient triangle + have an awkward scale
what are precautions during measurement?
check for zero error + measure the diameter of object @ 3 different locations and find average + avoid parallax error by placing line of sight perpendicularly to the scale marking + repeat experiment and take average readings + place thumb on stopwatch to minimise delay
what are precautions to take when using a pendulum bob?
ensure retort stand does not topple + set small angle of oscillation less than 10 degrees and use a constant small angle + pendulum oscillates along the vertical plane with no wobbling and no elliptical oscillations + ensure that the pendulum bob doesn’t;t hit the bench/point of suspension or retort stand + start timing only when oscillations are steady
what are precautions to take when measuring centre of gravity?
ensure holes are small so that only a small mass is removed + lamina must be hanging freely on the optical pin + optical pin should be parallel to the table surface
what is a precaution to take when measuring moments?
ensure ruler is balanced horizontally parallel to table surface
what are precautions to take when pin sighting (1-4)?
pins must be placed vertically upright + pins must at least be 5cm apart + use your fingers and move object pin slightly to check the image + ensure glass block is not shifted during the experiment
what are precautions to take when pin sighting (5-8)?
draw thin lines with a sharp pencil + eye is level with glass block when inserting pins + mark small holes using the pin and mark with small crosses and label the holes + position eyes at the same level as the pins
what are precautions to take when using a lens/ray box?
ensure lens set up is not shifted during the experiment + light from the illuminated object should pass through the centre of the lens + lens and screen and object should be aligned parallel to one another + lens must be upright so that image formed on the screen will be sharp
what are precautions to take when doing heat experiments (1-3)?
ensure that the mass is not touching the base of beaker during heating + ensures that the slotted mass is transferred as quickly as possible to minimise heat loss + stir the water with glass rod not with thermometer
what are precautions to take when doing heat experiments (4-7)?
place bulb of thermometer fully into the liquid + take readings only when temperature is steady + lose air hole when lighting Bunsen burners + read below for a concave meniscus and above for a convex meniscus
what are precautions to take when doing electricity experiments (1-4)?
remove switch in between readings to avoid draining the battery and increase resisstance because of heating effect + ensure the jockey is placed perpendicularly on the wire + do not exert too much pressure on the wire or slide the rheostat on the wire + try to straighten the wire to remove kinks
what are precautions to take when doing electricity experiments (5-8)?
connect all wires firmly to avid contact resistance + check zero error in voltmeter and ammeter _ connect the voltmeter and ammeter with the correct polarity + set rheostat at maximum value so that the experiment starts with the smallest current
what should sources of errors be?
not really/easily within your control
how do you minimize errors caused by human reaction time error?
change procedure (take the timing for a larger number of oscillations or take repeat readings for each set of values and find average to check on anomalous readings and reduce random error)
how do you minimize errors caused because of difficulty in pinpointing the exact moment an oscillation finishes?
change apparatus and use a photo gate in a datalogger to eliminate this error
how do you minimize errors in the readings of the effective length because the extension of the string?
change appartus and use an inextensible string of pendulum
how do you minimize errors in the readings of the effective length because of the extension of the string?
change apparatus and use an inextensible string of the pendulum
why is a ruler not being of uniform thickness a possible source of error?
it is difficult to balance the ruler at its midpoint
why is the plumbline and lamina moving whenever the ruler touches it a possible source of error?
it is difficult to measure x accurately as the ruler cannot be placed against the lamina
why are the ‘holes made in the lamina being too big’ a possible source of error?
it becomes difficult toe estimate and draw an accurate line through the exact centre of the hole to determine the exact position of the centre of gravity
how do you minimize errors caused by large holes being made in the lamina?
change apparatus and use thinner pins to make the holes and sharper pencils to draw thinner lines
why is the difficulty of judging the alignment of pins due to the thickness of the pin a possible source of error?
it can affect the measurement of the angle of reflection/refraction
how do you minimize errors caused by the difficulty of judging the alignment of pins due to the thickness of the pins?
change procedure (pins must be placed a t least 5 cm apart to help in judging the alignment of the pins) or change apparatus (use thinner pins)
why is pin holes being significantly large a possible source of error?
it makes accurate construction of incident and refracted/reflected/emergent rays more difficult and affecting the readings of the angle of incidence and the angle of refraction/reflection
how do you minimize errors caused by pin holes being significantly large?
change apparatus (use sharp pencil to draw the rays and thinner pins)
why is ‘the mirror being light and shifts light easily despite careful checks’ a possible source of error?
it affects the reading of the angle of incidence and angle of emergence
why is the ‘pins not being placed far apart due to the size of the trace’ a possible source of error?
it affects the drawing of emergent ray and affects the angle of emergence
why is ‘the glass block/prism have slightly curved edges’ a possible source of error?
it is difficult to replace the glass block/prism exactly at their outlined position each time and affecting the readings of the angle of incidence and the angle of reflection/refraction
how do you minimize errors from difficulty in identifying the exact position where the sharpest image is being formed affecting the measurement of the image distance?
change procedure (fine-tune by adjusting back and forth the screen to determine the sharpest image possible or take repeat readings and find average)
why isthe middle of the lens holder might not coincide with the centre of the lens a possible source of error?
it affects readings
why is the edge of the triangular object being uneven a possible source of error?
it makes it difficult to locate the position of the sharp image and affects the readings of the image distance
why are the images being large and not sharp a possible source of error?
it affects readings of the image distance
why are kinks in the potentiometer a possible source of error?
it makes it difficult to straighten and align against the metre rule and thus affects the readings of length
why is the potentiometer not having a uniform cross-sectional areaa possible source of error?
it affected the readings of measured diameter, current and voltage
why is the crocodile clip having a large surface area a possible source of error?
the point of contact at the 0cm mark might not be accurate
why are heating effects on potentiometer wire and connecting wires a possible source of error?
they affect the current and voltage readings
why is inconsistent contact/amount of pressure on the wire a possible source of error?
may affect current and voltage readings
how do you minimize errors from kinks in the potentiometer?
change procedure (try to straighten out the wire as much as possible before the experiment) or change apparatus (change wire/use a new wire each time)
how do you minimize errors from potentiometer not having a uniform cross-sectional area?
change procedure (take 3 sets of diameter readings to find average diameter for I and V)
how do you minimize errors from the large surface area of the crocodile clip?
change apparatus (use jockey stick to ensure sharp contact)
how do you minimize errors from the heating effect on wire?
change procedure (always open the switch when not taking reading + if the experiment is repeated , let the setup cool for while before repeating)
how do you minimize errors from inconsistent contact by jockey on wire ?
change procedure (try to exert the same amount of force and hold the jockey perpendicular to the wire to ensure sharp contact + take a few readings to find average reading of current and voltage)
why is heat lost to the surroundings a possible source of error?
it results in actual energy supplied to the experiment being less than its theoretical value and affects the accuracy of the results)
why is loss of water due to evaporation a possible source of error?
this will affect the results of experiments where the mass of water is used in the calculation
why is human reaction time a possible source of error?
affects the recording of timing
why is a constantly changing temperature a possible source of error?
it makes it difficult to read off accurately affecting the accuracy of the temperature reading s
why is temperature throughout the liquid not being uniform as stirring it is difficult with an object in the container a possible source of error?
affecting the readings of temperature of the liquid
why is the measuring cylinder expanding when hot water was poured into it a possible source of error?
this affectes the readings of the volume of the hot liquid
how do you minimize errors from heat loss to the surroundings?
change procedure (always transfer the liquid quickly to minimize heat loss + the experiment os repeated let the setup cool for awhile before repeating) or change apparatus (suggest various methods of lagging or insulation depending on the experimental setup
how do you minimize errors from loss of water due to evaporation?
change apparatus (use a lid to minimize evaporation)
how do you minimize errors from human reaction time?
use an electronic timer (datalogger) and temperature sensor
how do you minimize errors from a constantly changing temperature?
use a datalogger to record and monitor temperature change using a temperature sensor)
