Practical Skills I: Planning (Edexcel International A Level (IAL) Physics): Flashcards
Exam code: YPH11
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Define apparatus (in the context of an experiment).
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Cards in this collection (66)
Define apparatus (in the context of an experiment).
The apparatus is the equipment needed to carry out an experiment, including both what you are measuring and how you are measuring it.
Which instrument should be used to measure the diameter of a wire, and why?
A micrometer screw gauge, as it has the highest resolution for measuring small lengths.
Which instrument is designed for measuring the small extension of a wire?
A travelling microscope.
List the four measurements needed to determine the Young modulus of a wire using a hanging-mass apparatus.
Diameter of the wire
Initial length of the wire
Extension of the wire
Mass (or weight) of the hanging masses
A .......... would be the best choice for measuring the diameter of a wire, as it has a higher resolution than vernier calipers.
A micrometer screw gauge would be the best choice for measuring the diameter of a wire, as it has a higher resolution than vernier calipers.
True or False?
Vernier calipers are the best instrument for measuring the diameter of a thin wire.
False.
A micrometer screw gauge is better, as it has a higher resolution than vernier calipers for measuring small diameters.
Define range (of an instrument).
The range of an instrument is the highest and lowest value it can measure.
Define resolution (of an instrument).
The resolution of an instrument is the smallest increment it can measure.
How is the uncertainty of an analogue instrument, such as a ruler, related to its resolution?
The uncertainty is ± half the resolution, since a reading between scale divisions is estimated by eye from the midpoint.
Two digital thermometers read 80.13 °C and 42.0 °C. Which has the better resolution, and why?
Thermometer 1 (80.13 °C), because its smallest increment is 0.01 °C, compared with 0.1 °C for thermometer 2.
For a digital device, the resolution gives its ...........
For a digital device, the resolution gives its absolute uncertainty.
True or False?
The resolution given for an instrument in a textbook can always be assumed to apply in an exam question.
False.
Exam questions may give a different resolution (e.g. an ammeter with 0.2 mA). Always use the value given in the question rather than assuming a typical value.
Define calibration.
Calibration is a comparison between a known measurement and the measurement obtained using an instrument, used to check the instrument's accuracy.
Why might a meter, such as a voltmeter, be checked to see if it reads zero before taking measurements?
To check for a zero error, which would otherwise introduce a systematic error into every reading.
What is a calibration curve used for?
To convert measurements made on one scale (e.g. e.m.f of a thermocouple) into another scale (e.g. temperature), when an instrument's output is not proportional to the quantity being measured.
Give an example of two sensors whose output is not proportional to the quantity they measure, requiring a calibration curve.
A thermocouple (e.m.f against temperature) and a thermistor (resistance against temperature).
The accuracy of a measuring instrument .......... over time, typically due to normal wear and tear.
The accuracy of a measuring instrument degrades over time, typically due to normal wear and tear.
True or False?
A voltmeter with a systematic error that increases with voltage produces a calibration curve that passes through the origin.
False.
Since the voltmeter reads greater than the true value even at zero, the calibration curve does not pass through the origin (0,0).
Which instrument would you use to measure the current through a bulb?
An ammeter.
Which instrument provides a monochromatic, coherent light source, useful for investigating interference?
A laser.
What is the key factor to consider when choosing an instrument to measure a variable?
Its resolution — if the resolution is too big, the instrument won't be able to measure small measurements.
Define oscilloscope, in terms of its use in experiments.
An oscilloscope displays waves and is used to measure their frequency.
For measuring a length between 0.01 mm and 0.1 mm, you should use a ...........
For measuring a length between 0.01 mm and 0.1 mm, you should use a micrometer screw gauge.
True or False?
Vernier calipers are the most appropriate instrument for measuring the diameter of a thin wire.
False.
Vernier calipers have a resolution of 0.1 mm, whereas a micrometer screw gauge (0.01 mm – 0.1 mm) is more appropriate for very short lengths, such as a wire diameter.
Define independent variable.
The independent variable is the only variable that should be deliberately changed throughout an experiment.
Define dependent variable.
The dependent variable is the variable that is measured to determine the outcome (results) of an experiment.
Define fair test.
A fair test is one in which only the independent variable is allowed to affect the dependent variable.
When investigating Charles' law, identify the independent, dependent and control variables.
Independent: temperature
Dependent: volume
Control: pressure and number of moles
Why is temperature often a control variable in circuit experiments, unless a thermistor is being used?
Because the temperature of a wire or component increases as current flows through it over time, which would otherwise affect the results.
If control variables are not kept constant, they could affect the results of an experiment, making them ...........
If control variables are not kept constant, they could affect the results of an experiment, making them unreliable.
True or False?
Describing a control variable as the 'amount' of water is an acceptably precise way to record it.
False.
Scientific terms should be used, such as volume of water, since 'amount' is not a precisely measurable quantity.
Define anomalous result.
An anomalous result is a result that does not fit in with the pattern of the other readings.
Why are repeat readings taken in an experiment?
Improves the accuracy of a measurement
Makes the data reliable
Allows anomalous results to be identified
Why might repeat readings be impractical for an experiment involving electrical components that heat up?
The components would need to be disconnected to cool down between each reading, and the whole experiment repeated — this could take too long across a wide range of readings.
How many times are readings typically repeated in an experiment, and over how many values of the independent variable?
Readings are typically repeated three to five times, across five to ten different values of the independent variable.
The average value of a variable should always be found from the .......... to use in further calculations.
The average value of a variable should always be found from the repeat readings to use in further calculations.
True or False?
It is always best practice to take repeat readings immediately, one after another, in every experiment.
False.
For experiments where conditions change between readings (e.g. heating components, or time-dependent variables), taking repeats immediately could make it an unfair test.
Why should the power supply be turned off between readings in an electrical circuit experiment?
To prevent components (especially thin wires) becoming too hot, which could cause a burn or affect the results by changing their resistance.
Why should a support stand be clamped or weighted when using masses, wires or springs?
To prevent the stand from falling over.
Why should a soft surface, such as a cushion, be placed underneath a falling object (e.g. a ball bearing used to calculate g)?
To protect the surface below from damage.
Why should liquids be kept away from electrical circuit apparatus?
Spilled liquid near electrical apparatus could cause a fire.
How should hot glass apparatus be handled after an experiment such as measuring specific heat capacity?
Allow it to cool down, or wear gloves when handling it.
True or False?
Safety goggles are only needed in physics practicals when handling chemicals.
False.
Goggles are also required for other hazards, such as when using wires, in case one snaps under tension.
When using electrical circuits, do not exceed the rating for any appliance in the circuit.
When using electrical circuits, do not exceed the voltage rating for any appliance in the circuit.
Define standard form.
Standard form is a way of writing a number as a value multiplied by a power of ten, making very large or very small numbers easier to present without repeating many zeros.
When calculating a mean value from repeat readings, how many significant figures should be used compared to the raw readings?
It is acceptable to increase the number of significant figures by one compared to the raw readings.
What significant figure rule must be followed for data recorded within a single column of a results table?
All the data in a column should be quoted to the same number of significant figures.
In the equation of a straight line y = mx + c, what can the gradient and y-intercept be used for when a relationship obeys this form?
They provide values that can be analysed to draw conclusions about the relationship between the two plotted variables.
When verifying the inverse square law for gamma radiation, why is background radiation subtracted from each count rate reading?
To obtain the corrected count rate, C, which removes the contribution of background radiation not due to the source.
True or False?
Estimating the area under a non-linear graph is not a graph skill required in A Level Physics.
False.
This is a required skill, alongside drawing tangents, calculating gradients and understanding where asymptotes may be required.
A straight-line graph that passes through the origin shows that the two plotted variables are proportional.
A straight-line graph that passes through the origin shows that the two plotted variables are directly proportional.
Define uncertainty.
Uncertainty is an estimate of the difference between a measurement reading and the true value; the interval within which the true value can be considered to lie with a given level of confidence.
Define a systematic error.
A systematic error arises from a faulty instrument or a flaw in the experimental method; it is repeated consistently every time and affects the accuracy of all readings.
How does a systematic error appear on a straight-line graph that is expected to pass through the origin?
The line of best fit is offset from the origin on the y- or x-axis by a constant amount, equal in size to the systematic error.
Why is measuring the time for ten oscillations and dividing by ten more accurate than timing a single oscillation?
It reduces the effect of human reaction time on the measurement, since the timing error is spread across ten oscillations rather than affecting one single reading.
Give two ways to reduce the uncertainty in a measurement.
Take repeat readings (about three to five) and calculate the mean
Use the appropriate piece of apparatus for the measurement (e.g. a micrometer for a small distance, rather than a ruler)
Which types of measurement tend to produce the largest uncertainties?
Extremely small or extremely large measurements, and those that are most subjective to read (e.g. distinguishing between blurry lines in a diffraction pattern).
True or False?
Uncertainty and error mean the same thing in a physics practical.
False.
An error is the difference between a measurement and the true value, whereas uncertainty is the estimated range within which the true value is expected to lie.
To reduce a systematic error, instruments should be , or different instruments should be used.
To reduce a systematic error, instruments should be recalibrated, or different instruments should be used.
Define an implication of physics.
An implication is a consequence of scientific knowledge, which may be commercial, legal, ethical or social.
Give the four types of implication that scientific knowledge may have.
Commercial, legal, ethical and social implications.
Give an example of an ethical implication when building a new power station.
Whether it is safe for the wildlife living in the surrounding area.
Why must scientific evidence be thoroughly tested and trusted before society uses it to make decisions?
Most people making decisions based on the evidence (e.g. policy makers and politicians) are not scientists themselves, so they must be able to trust the research on which their decisions are based.
Give an environmental factor associated with wind farms, despite them being a cheap and sustainable energy source.
Wind turbines can harm birds and bats.
True or False?
Economic factors in scientific decision-making only concern the initial cost of research.
False.
Economic factors also weigh up long-term benefits, such as reduced carbon emissions, against the cost of the research or new technology.
factors are considered for decisions that affect people's daily life, such as noise pollution.
Social factors are considered for decisions that affect people's daily life, such as noise pollution.
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