ATP- Paper 6 Flashcards
Suggest why it is more accurate, when using a ruler, to measure D for five marbles rather than measure the diameter of a single marble.
effect of uncertainties reduced
diameters of marbles vary
Describe how the student uses the two blocks and the marble to determine a new accurate value for the diameter of a marble.
Draw a diagram to show the arrangement.
Describe clearly how the student ensures that the value for the diameter of a marble is as accurate as possible.
use marble between two blocks and measure gap 1
suitable means of ensuring accuracy e.g.:
measure gap in at least two places and check equal to ensure blocks are parallel /
rotate marble to different axis and take average of measurements
cylinder inaccuracy- source and improvement
graduations on measuring cylinder too large /
use smaller measuring cylinder or greater number of marbles /
State two variables which must be controlled so that the comparison of x1 and x2 is valid. (temperature change over time)
same volume of water,
same material / thickness / surface area shape of beaker,
same room temp / named appropriate environmental condition
Suggest one practical reason why students carrying out this experiment may not obtain the same readings as in Table 3.1. Assume that the procedure has been done carefully. (resistance calculation by length of wire)
difficult to position crocodile clip accurately /
inconsistent connection with crocodile clip /
resistance wire not uniform
Describe the main difficulty that a student has when doing this experiment as accurately as possible. (balancing of a meter ruler on a pivot)
Using apparatus from Fig. 1.1, explain briefly how you would determine the position of the centre of mass of the ruler.
difficulty in obtaining exact balance
OR judging position of (centre of) load
OR masses sliding on ruler
balance ruler (on pivot with no loads).
pivot point is read / balance point shows centre of mass
A student states that the average rate of cooling of the water decreases as the temperature comes nearer to room temperature.
(i) Suggest one change to the experiment that you could make to test the statement.
(ii) Suggest how to display the results to make it easier to see the trend in the rate of cooling.
(e) Explain briefly why it is good practice to read the thermometer scale at right angles
2(d)(i) continue taking temperatures / continue for a longer time (until close to room temperature)
OR use lower / higher starting temperature (of water)
2(d)(ii) plot a graph
of temperature against time OR cooling rate against time / temperature
2(e) to avoid parallax error
State one precaution that you would take in order to produce an accurate ray trace.
Suggest one reason why different students, all doing this experiment carefully, may not obtain identical results.
In order to investigate further a possible relationship between values of (α + β), more values
are required. Suggest values of the angle of incidence α that the student could use. (pins are placed on this line)
view bases of pins
place pins (as) far apart (as possible) / > 5 cm apart
ensure pins are vertical
sharp pencil / thin lines / thin pins
difficult to align pins / place pins accurately / pins (too) thick. (getting pins vertical, lining up the pins exactly, drawing accurate thin lines), thickness of lines and mirror
at least 1 value < 30(°) and 1 value > 45(°) 1
all recorded values less than 90°
A student states that the water cools slowly. Suggest two changes to the experiment that the student makes to increase the rate of cooling of the hot water without changing the starting temperature of the hot water. Room temperature remains constant.
remove lid
thinner lid
paint the beaker black
stir the water
change beaker to container that is a better conductor / named metal- can
increase surface (area of water / beaker)
use a wider beaker
blow air over water surface / use a fan
use a smaller volume of water
State one precaution that you would take to obtain accurate temperature readings. Explain briefly the reason for this precaution.
statement: view thermometer / scale / reading at right angles / eye level
explanation: to avoid parallax error
statement: stir (before taking reading)
explanation: to distribute water evenly / to ensure that all the water is at the same temperature
statement: ensure thermometer does not touch the side / base of beaker
explanation: temperature different to that of the bulk of the liquid
statement: wait until the thermometer (reading) stops rising at the start
explanation: so that the maximum temperature of the liquid is recorded
The student uses a measuring cylinder to measure 200cm3 of water. He takes the reading from the bottom of the meniscus. Explain the reason for taking the reading at the bottom of the meniscus rather than at the top of the meniscus.
negligible / very small volume / amount of water between the bottom and the top of the meniscus
A student suggests that angle β should be equal to the angle of incidence i = 20°.
State whether your result supports the suggestion and justify your answer. (yes)
YES
explanation of idea of beyond limits of experimental accuracy
e.g. values close (enough) / not too far apart / < 10% difference
if values are equal, it is sufficient to say just that the values are equal
Describe a technique for ensuring that the ruler is as near as possible to being balanced
idea of allow to (just) tip one way then the other way
Briefly explain one advantage of using a variable resistor to determine the resistance of resistor U rather than the procedure carried out in (b) and (c).
A student suggests that potential difference and current for resistor U are proportional. State how a graph of potential difference against current for resistor U can confirm this
suggestion.
can obtain continuous set of values /
more straightforward to change current /can obtain more values easily
straight line and through origin
It is sometimes difficult to position the load W on the scale of the metre rule at the correct distance d from the pivot. Suggest one change to the apparatus to overcome this difficulty.
Suggest one possible source of inaccuracy other than the difficulty described in (d)(i). Assume that the experiment is carried out carefully.
suspend load from loop of thread / any other suitable method to avoid standing load over marks on rule
valid source of uncertainty e.g. test load not exactly 1.0
N / spring extension not linear / metre rule not uniform
The student records the volume V to the nearest 1cm3.
Suggest why this is appropriate.
measuring cylinder can only be read to nearest 1 or 2 cm3.
to nearest cm3 means you are measuring the volume to 3 significant figures (which is sufficient)
A student thinks the three resistors RA, RB and RC have the same resistance within the limits of experimental accuracy.
(i) Suggest how the student could use the apparatus provided to test his idea.
use of a voltmeter and/or an ammeter
measure V and I for each resistor and calculate R
OR connect each resistor to the same voltage supply and measure the current
OR connect resistors in series and measure the voltage across each of them
OR connect resistors in parallel and measure the current through them
State two precautions that you would take to obtain accurate readings in this experiment. (A student determines the focal length f of a lens- triangle).
use darkened room / bright(er) object
move lens slowly (to find sharpest image)
move lens back and forth (to find sharpest image)
ensure that object, lens and screen are vertical
object and (centre of) lens same height (above bench)
perpendicular reading / viewing of the ruler scale
mark the centre of the lens on its holder
(i) Suggest a suitable number of sets of readings that the student should take. and why
(ii) Explain briefly how this graphical method can give a more accurate value for the focal length.
any integer between 5 and 15 (inclusive)
greater accuracy / easier to line up pins
(a straight line) is a way of taking an average
anomalous results can be seen (and repeated or ignored)
Another student does this experiment with the same starting temperature but in a room with a much higher room temperature than θR from (a)(i). State how this affects his value of x in d(i). Explain your answer by reference to the results in Table 2.1 for the beaker with 50cm3 of hot water.
(e) Some thermal energy is lost from the sides of the beaker.
The student wishes to find out how much this loss of thermal energy affects the cooling rate of 50cm3 of water. Briefly describe an additional experiment that the student can carry out to investigate this. Explain how the results can be used to determine how much this loss affects the cooling rate.
value of x will be less/lower
temperature difference between beaker and room is less and values from table referred to
repeat experiment with a lid
(calculate cooling rate) subtract from x to find cooling rate without transfer from sides OR a comparison of cooling rates
Describe one difficulty when measuring the height of the image in this type of experiment. Suggest an improvement to overcome this difficulty. (triangle)
hand/ ruler gets in way of light
mark on screen and measure later OR
use screen with scale OR
use translucent screen and measure at rear
screen can move when measuring- clamp screen in place
Suggest a suitable distance apart for pins P1 and P2 for this type of ray-trace experiment.
P1 P2 distance at least 5(.0) cm and no larger than 15(.0) cm
greater accuracy / easier to line up pins
In order to investigate further a possible relationship between values of (α + β), more values are required.
Suggest values of the angle of incidence α that the student could use.
at least 1 value < 30(°) and 1 value > 45(°)
all recorded values less than 90°
A student wishes to determine the resistance of the lamp RL when the potential difference across the lamp VL = 0.0V.
Describe how the experiment can be extended to do this with the help of a suitable graph.
obtain more values
and plot a graph of RL vs VL extend line to RL axis and read intercept
