Practical

Question 1

oscillations

Suggest how the procedure can be improved to increase the accuracy of the result.

Answer 1

time a greater number of oscillations, so timing errors have less effect

Question 2

The ammeter is not broken.
Suggest what the student may have done incorrectly while setting up the circuit.

Answer 2

diode causes current to flow in the wrong direction

Question 2

ray trace

The measurement of a quantity is reproducible if a similar result is obtained when the measurement is repeated by a different method or under different conditions.

Suggest how the student can adapt this experiment to check if the value of d/1 is reproducible.

Answer 2

repeat with optical pins OR
repeat with  = 60 on the other side of the normal

Question 3

How to obtain more reliable readings.

Answer 3

repeat each reading and calculate an average value

Question 3

How to accurately measure the volume of liquid in a measuring cylinder

Answer 3

Read below meniscus.
Line of sight perpendicular to the scale.

Question 3

How to measure diameter of a rod

Answer 3

Use of rod between two blocks and measure gap in at least 2 places, ensuring blocks are paralell and take average. Use a micrometre.

Question 3

Explain briefly why the position of the pivot may not be exactly at the 50.0 cm mark of the rule.

Answer 3

center of mass of ruler not at the center

Question 3

Precautions while measuring volume of wooden rod →

Answer 3

Wood might absorb
water, measuring cylinder scale not precise

Question 3

Why it is useful to take a trial reading for a experiment?

Answer 3

to check if dependant is measurable, to check if independant value is appropriate. (Can be measured accurately) Set a good range of d and t values.

Question 4

How to ensure if scale is horizontal?

Answer 4

Measure the distance between the metre rule and bench in two different places, If the distances are equal, the metre rule is horizontal.

Question 4

It is difficult to position the load 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.

Answer 4

Measure length of one side, halve, mark point.
suspend load from loop of thread
align with mark on rule

Question 5

How to make sure the length, l of the pendulum bob is as accurate as possible →

Answer 5

Measure the top and bottom of bob and average
View perpendicular to the scale
Rule parallel with string. Use of set-square
Keep the rule close to the pendulum

Question 6

How to get temperature reading from a thermometer as accurate as possible?

Answer 6

Line of sight perpendicular to scale.
Stir mixture before.
Wait for it to stop rising at the start, so the max is recorded.
Comparison - keep the thermometer at same depth
don’t let thermometer touch the bottom/sides of the container

Question 6

loads and springs

What is the source of inaccuracy
in this experiment →

Answer 6

test load not exactly 1.0 N /
spring extension not linear /
metre rule not uniform

Question 6

What are the control variable while measure the rate of cooling/heating of water in a beaker →

Answer 6

Same volume of water
Same initial + room temperature
Same SA, material, and height of container
Same duration of experiment

Question 7

How to reduce loss of thermal energy from beaker →

Answer 7

insulation
lid
lower starting temperature
higher room temperature
smaller volume of water
smaller surface area

Question 8

Experient for how lid affects the rate of cooling.

Answer 8

Repeat same experiment
without a lid. calculate cooling rate and subtract cooling rate with lid.

Question 9

Possibile errors in ray trace experiments →

Answer 9

lines not thin, draw thin lines using sharp pencil
Difficulty to align pins, view bases of pins

Pins too thick, use thin pin
Inaccuracies have more effect on small angl

ensure pins are far apart and upright

Question 10

Why 2.7cm pin separation is not suitable →

Answer 10

pin separation should be as large as
possible for greater accuracy

Question 11

What are the possible difficulties in resistance wire experiments →

Answer 11

Difficulties to judge position of crocodile clips
Difficult to measure wire to nearest mm
Difficult to figure out readings on meters between marks

contact between not precise

Question 12

How must a variable resistor be placed with reference to resistance wire?

Answer 12

in series

Question 13

Precautions in lens experiments →

Answer 13

Darkened room
Moving screen slowly to obtain best image

Mark block to show centre of lens
Clamp rule to bench

Lens and object and screen upright
Lamp, lens, object at same height

Question 14

Describe how the experiment can be extended with the help of a suitable graph.

Answer 14

Obtain more values. Plot a graph (axis specified). Extend the line to R axis and read intercept.

Question 15

The student adjusts the position of the metre rule until it is near as possible to being balanced. Describe a technique.

Answer 15

Find the point where it tips to one side and the point where it tips to the other. Between these points is the balance point.

Question 16

How to obtain the sharpest image?

Answer 16

Move the screen back and forth slowly.

Question 17

Difficulty experienced when using ruler to measure height of image.

Answer 17

Ruler and hand gets in the way of light and makes shadows. Use a translucent screen and measure from the back of the translucent screen/paper.

Question 18

# light trace Suggest a distance.

Answer 18

5 | 5-15

Question 19

# light traces Investigate the relationship further.

Answer 19

many values above and below

Question 20

Suggest how to test that the centre of mass is at 50cm indeed.

Answer 20

Without mass. Read position at which it is near as being balanced as possible.

Question 20

Advantage of variable resistor compared to calculating R.

Answer 20

Easier to change current to certain chosen values. Easy to obtain more values and to set a large range of values.

Question 20

Testing if values are directly proportional.

Answer 20

Plot graph. *specified calculate T/D

Question 21

# temperature Suggest how to continue the experiment to support the suggestion.

Answer 21

more readings until room temperature

Question 22

Why is it more accurate to measure 5 marbles?

Answer 22

The effect of uncertainties is reduced.

Question 23

Improvement to displacement method.

Answer 23

graduations on measuring cylinder is too large -> use a smaller measuring cylinder, greater number of marbles

Question 24

Write a conclusion on the cooling.

Answer 24

greater overall temp change at A than B, because starting temperature is greater, (reference to values) compare times taken to reach a fixed temp drop

Question 25

# combined resistance Vs combined resistors Explain how to extend the investigation to further investigate the relationship.

Answer 25

Use another resistor. Add at least three more resistors (one at a time)

Question 26

Possible sources of inaccuracy in apparatus + sand.

Answer 26

sand surface not flat balance only to nearest gram metre rule not uniform

Question 27

# volume of sand particles Explain why method one is not suitable.

Answer 27

Air gaps between sand add to the volume, so it appears bigger than it is.

Question 28

How to reduce the effcet on cooling rate?

Answer 28

water bath

Question 29

Changes to increase cooling rate.

Answer 29

remove lid use smaller volume | thinner lid, stir water, beaker that is a better conductor (paint black)

Question 30

Explain the reason for taking the reading at the bottom of the meniscus.

Answer 30

Amount of water between the top and bottom of the meniscus is negligible.

Question 31

# ball and metre rule Distance from ball to start of metre rule?

Answer 31

end-end=2 2/2=1 end 1 + 1= result | starting end to centre of ball

Question 32

# x-axis is light intensity, y-axis is resistance of LDR What is the control variable?

Answer 32

type of light source, angle of light source relative to LDR, p.d

Question 33

Measure distance deflected by wooden strip?

Answer 33

ruler

Question 34

# deflection of wooden strip by load What are the controls?

Answer 34

type of wood, length and width of wooden strip, humidity

Question 35

# force to break different metal wires How many metals to mention? Describe repeat.

Answer 35

3, repeat for new values of independant variable (the other two metal wires)

Question 36

Suggest why the value of VA is only an approximation of the volume of the block.

Answer 36

difficult to measure irregular dimensions, repeat in several places for each dimension and take averages

Question 37

Method 1: volume using formula, balance for mass Method 2: volume using displacement, force Which will give a more accurate density?

Answer 37

2) volume is measured directly

Question 38

A student decides to continue the experiment using larger values of u. Explain why this produces less accurate values for W.

Answer 38

b, which is used to calculate is too small, difficult to measure

Question 39

# metre rule, pivoy, load Suggest one practical reason why it is difficult to obtain exact results with this experiment.

Answer 39

difficult to achieve balance

Question 40

The student notices that the lamp does not glow when he takes the final set of readings. He thinks that the filament has broken. State whether the student is correct and give a reason for your answer

Answer 40

No, there is a current reading

Question 41

A student suggests that the resistance R of the lamp filament should be constant. Suggest, referring to the observations, a reason why the resistance R may not be constant in this experiment.

Answer 41

filament changes brightness, change in temperature

Question 42

Suggest one practical reason why measuring the time for 200 oscillations, rather than 20 oscillations, may not be suitable.

Answer 42

student may lose count

Question 43

Suggest a practical reason why the result obtained from the experiment may be different. (pendulum)

Answer 43

student did not react fast enough when starting and stopping stopwatch, difficulty measuring accurately from the centre of the bob

Question 44

Suggest two improvements to the experiment. (pendulum)

Answer 44

use of different lengths, repeat timing, increased number of oscillations

Question 45

Why angle i is NOT equal to angle r in ray experiment:

Answer 45

Thickness of pins Thickness of mirror Protractor is not precise

Question 46

Inaccuracy of ray box method

Answer 46

thickness of rays.

Question 47

Centre of mass experiment (with the lamina):

Answer 47

You view the string directly in front of the card.

Question 48

Minimizing the heating effect of a current

Answer 48

Decrease voltage Decrease the resistance of a resistor

Question 49

How to check if a rule is vertical

Answer 49

use a set square

Question 50

Variables in experiments about springs and stretching effect:

Answer 50

Number of coils Length of spring Diameter\thickness of spring or wire Selection of loads

Question 51

Improvement made to calculating circumference by string method Avoid parallax error

Answer 51

Thinner string Parallel winding of springs

Question 52

Precautions for circuit readings of I and V so that they are accurate

Answer 52

For I specifically: Limit current so that temp. doesn't increase Use a tapping meter For I and V: Switch off between readings.

Question 53

Fair test for pendulum experiments

Answer 53

Length of pendulum Shape of bob No. of swings Amplitude

Question 54

Precautions and procedures in electrical experiments

Answer 54

check for a zero error Always check polarities before closing the switch (completing the circuit)