Pearson Edexcel International A Level Physics: Unit 3: planning and checking an experiment (YPH11) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions follow the Pearson Edexcel International Advanced Subsidiary/Advanced Level in Physics (YPH11) specification, Issue 3, sections 3.3 Planning and 3.4 Implementation and measurements. Unit 3 is an International AS (IAS) unit on the experiments of Units 1 and 2. Read the study guide and revision notes first. The course home is the Edexcel A Level Physics hub, with a printable checklist.

Questions

1. Name the most suitable instrument, and give its resolution, for measuring (i) the diameter of a wire of about 0.60 mm, (ii) the diameter of a steel ball of about 12 mm, (iii) the height from which a ball is dropped, about 1.5 m. [3]

2. Vernier calipers show 27 mm on the main scale, with the fourth Vernier mark aligned with a main-scale mark. State the reading, the uncertainty in this single reading and the percentage uncertainty. [3]

3. A micrometer is closed on nothing and reads -0.03 mm. It is then used on a wire. The sleeve shows 0.5 mm and the thimble line at 38.

(a) State the uncorrected reading. [1] (b) Calculate the diameter of the wire. [2] (c) Explain why the answer is given to two decimal places. [1]

4. A voltmeter reads 0.04 V when disconnected from any circuit.

(a) State the type of error and why repeating does not remove it. [1] (b) Correct the readings 0.52 V and 0.96 V. [1] (c) Find the percentage of the first reading that the error represents. [1]

5. A student times a ball falling 0.80 m through oil. The times are 2.41 s, 2.38 s, 2.44 s, 3.10 s and 2.40 s.

(a) Identify the anomalous reading and suggest a cause. [2] (b) Calculate the mean of the remaining readings. [1] (c) Give the uncertainty in the mean as half the range, and the percentage uncertainty. [2]

6. A long steel wire is stretched with slotted masses of up to 8 kg to find the Young modulus. Identify two hazards and a precaution for each. [4]

7. In a falling-ball experiment the time for a ball to fall through glycerol is measured at different temperatures.

(a) State three variables to control. [3] (b) Explain why temperature is the independent variable and not just a control here. [1]

8. A student loads a spring and records these results. Masses: 50 g, 100 g, 150 g and 200 g. Extensions: 1.0 cm, 2.1 cm, 3.0 cm and 4.05 cm. A ruler marked in mm is used.

(a) Comment on the number of readings. [2] (b) Comment on the range of the loads. [2] (c) Comment on the significant figures. [2]

9. A student measures the potential difference V across a cell for different currents I. Currents: 0.10, 0.20, 0.30, 0.40 and 0.50 A. Potential differences: 1.44, 1.38, 1.32, 1.62 and 1.20 V.

(a) Use the points at 0.10 A and 0.50 A to find the gradient, then predict V at 0.40 A. [2] (b) Comment on the recorded value at 0.40 A. [1] (c) Suggest two checks to make before deciding what to do with the point. [2]

10. A student measures the extension of a hanging spring by holding a metre rule beside it. Suggest two improvements, each with the reason it helps. [4]

11. Plan an experiment to determine the acceleration of free fall using a steel ball, an electromagnet release and an electronic timer. Describe the apparatus and procedure, how you will control the variables, how you will deal with a hazard, how you will use the data, and one source of systematic error. Comment briefly on one benefit or risk of the physics in a wider context. [10]

12. A student plans to find the resistivity of a constantan wire of diameter about 0.45 mm. She measures the diameter once with a ruler marked in mm, uses a single length of 50 cm, leaves the current on throughout, and records the ammeter reading as 1 A.

(a) Calculate the percentage uncertainty in the diameter using half the ruler’s resolution, and compare it with a micrometer measurement (resolution 0.01 mm). [3] (b) Comment on the single length. [1] (c) Explain the problem with leaving the current on. [2] (d) Comment on the ammeter reading. [1] (e) Describe how she should use the data. [2]

Answers

1. (i) Micrometer screw gauge, 0.01 mm [1] (ii) Vernier calipers, 0.1 mm [1] (iii) metre rule (or tape), 1 mm [1] [3] Examiner insight: answers that give the instrument and its resolution together are easier to credit than the instrument name alone.

2. Reading = 27 + 4 × 0.1 = 27.4 mm [1]. Uncertainty = half the resolution = 0.05 mm [1]. Percentage = 0.05 ÷ 27.4 × 100% = 0.18% [1] [3] Examiner insight: write the percentage to one or two significant figures; a long string of digits adds nothing.

3. (a) 0.5 + 0.38 = 0.88 mm [1] (b) The zero error is negative, so the true diameter is larger [1]: 0.88 + 0.03 = 0.91 mm [1] (c) The micrometer resolves 0.01 mm, so readings are recorded to the nearest 0.01 mm [1] [4] Examiner insight: the direction of the correction is the usual slip; say whether the error is positive or negative before correcting.

4. (a) Systematic, because every reading is shifted by the same amount [1] (b) 0.52 − 0.04 = 0.48 V and 0.96 − 0.04 = 0.92 V [1] (c) 0.04 ÷ 0.52 × 100% = 7.7% [1] [3] Examiner insight: name the type of error and give the reason in the same sentence, since “systematic” alone is a label rather than an explanation.

5. (a) 3.10 s is far from the others [1]; the stopwatch may have been started or stopped late (reaction time), or the ball touched the side [1] (b) Mean = (2.41 + 2.38 + 2.44 + 2.40) ÷ 4 = 2.41 s [1] (c) Half range = (2.44 − 2.38) ÷ 2 = 0.03 s [1]; percentage = 0.03 ÷ 2.41 × 100% = 1.2% [1] [5] Examiner insight: give a reason for dropping a reading, and make clear which readings the mean uses.

6. Hazard 1: the wire may snap and whip [1]; precaution: goggles and a cloth over the wire, or keep to loads within the limit [1]. Hazard 2: heavy masses may fall on feet [1]; precaution: a sand tray under the masses and feet kept clear [1] [4] Examiner insight: each hazard is better paired with its own precaution than listed together.

7. (a) Any three of: the same ball [1]; the same liquid sample and depth [1]; the same distance timed [1] (any other control linked to fall time also earns credit) (b) The viscosity of glycerol changes with temperature, so it affects the fall time and is the variable being studied [1] [4] Examiner insight: controls need to be linked to the effect on the fall time, not named alone.

8. (a) Only four readings [1]; too few to see the pattern or judge whether the last point is anomalous, so use at least six [1] (b) The range is small, 50 g to 200 g [1]; a wider range (until near the limit of proportionality) would fix the gradient better [1] (c) Extensions should have the same number of decimal places as the ruler’s resolution [1]; 4.05 cm cannot be read on a mm ruler, so should be 4.0 or 4.1 cm [1] [6] Examiner insight: tie each comment to the data, such as the value 4.05 cm, and say what would improve it.

9. (a) Gradient = (1.20 − 1.44) ÷ 0.40 = -0.60 V A⁻¹ [1]; at 0.40 A the line gives 1.44 − 0.60 × 0.30 = 1.26 V [1] (b) The recorded 1.62 V is 0.36 V above the line, probably the digits of 1.26 transposed [1] (c) Re-read the meters and repeat the reading [1]; check the connections and the calculation for slips [1] [5] Examiner insight: checking and repeating usually comes before excluding, and the check should be named.

10. Use a set square against the ruler to make sure it is vertical [1], as a tilted rule overestimates the extension [1]. Put a pointer or marker on the spring and read at eye level [1] to avoid parallax [1] [4] Examiner insight: “be more careful” is not credited; the improvement should name apparatus and say what it fixes.

11. Apparatus: electromagnet and clamp, steel ball, trapdoor or light gate, timer, metre rule or tape, stand [1]. Measure height h from the base of the ball to the trapdoor, with the rule checked vertical [1]. Release by switching off the magnet so the timer starts, and stop it at impact [1]. Repeat each height three times and average the times [1]. Use at least six heights over a wide range [1]. Hazard: falling ball and stand, so use a clamped stand with a soft landing or a tray [1]. Data: plot h against t²; since h = ½gt², the gradient = g ÷ 2 [1] and g = 2 × gradient [1]. Systematic error: residual magnetism delays release, so every measured time is too large and g is underestimated; fit a non-magnetic spacer or use a light gate release to reduce it [1]. Context: accurate g values help in geophysical surveys that locate dense rocks, but fieldwork has energy costs [1] [10] Examiner insight: lists of apparatus alone gain little; credit builds up when each stage says how the quantity is measured and how it is used.

12. (a) Ruler uncertainty = 0.5 mm [1]; percentage = 0.5 ÷ 0.45 × 100% = 111% [1]; micrometer: 0.005 ÷ 0.45 × 100% = 1.1%, so it is about one hundred times smaller [1] (b) One length gives no trend; take several lengths and plot R against l [1] (c) The wire heats, so its resistivity changes, and readings drift [1]; use a low current and switch off between readings [1] (d) One significant figure is too coarse; record to the meter’s resolution, for example 0.52 A [1] (e) Plot R against l; the gradient equals ρ ÷ A [1]; ρ = gradient × (π × d² ÷ 4) [1] [9] Examiner insight: working out the percentage uncertainty makes the case for the micrometer far more persuasive than the statement that it is better.

Where marks are usually lost

• Giving an instrument name with no resolution when the question asks for both.
• Missing the sign of a zero error and correcting the wrong way.
• Calling a fixed offset random, or saying repeating removes it.
• Quoting readings to more decimal places than the instrument can show.
• Listing hazards with no precaution paired to each one.
• Describing controls without saying why they affect the result.
• Naming an improvement without the apparatus, or “more accurate” without the instrument.
• Describing a graph without saying what the gradient represents.
• Removing an anomalous point without a check.

Next steps

• Revisit the revision notes and the study guide.
• Back to the Edexcel A Level Physics hub and the checklist.
• Try all free 10-minute diagnostics.
• Book a free trial class: trial.

Official syllabus

Pearson Edexcel International Advanced Subsidiary/Advanced Level in Physics, specification Issue 3 (July 2021), Pearson Education Limited: Unit 3 sections 3.3 and 3.4, with Appendix 10 on uncertainties and practical work.