Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

1.2.6Development of Practical Skills in Physics

Presenting in a Scientific Way

5 min read 9 parts Lesson 13 of 29 1 quiz

0%read
Lesson summary

1.2.6 Presenting in a Scientific Way — OCR A Level Physics A notes: Use SI units, prefixes, standard form, correct symbols and clear scientific language and diagrams when reporting practical work.Science depends on clear communication: another physicist should be able to read you…

  • significant figures
  • Worked example 1
  • Worked example 2
  • Worked example 3
  • Control variable
  • In calculations write the equation first, substitute values with units, then the answer with its unit

Section 1 of 9Communicating like a physicist

Science depends on clear communication

  • another physicist should be able to read your report, understand exactly what you did and repeat it.
  • That requires precise vocabulary, consistent units, sensible numbers and clean diagrams.
  • These conventions are also marked directly in practical assessments.

Section 2 of 9SI units and prefixes

Physics uses the SI system.

SI units and prefixes
The base units that appear most are metre (m), kilogram (kg), second (s), ampere (A) and kelvin (K).
Derived units are built from these: newton (N = kg m s−2), joule (J = N m), watt (W = J s−1), pascal (Pa = N m−2).
Use the index form (m s−1) rather than a slash.

Prefixes keep numbers readable:

PrefixSymbolFactor
nanon10−9
microμ10−6
millim10−3
kilok103
megaM106
gigaG109

Convert to base units before calculating

  • 4.5 mm = 4.5 × 10−3 m;
    • 250 μA = 2.5 × 10−4 A.
  • Take care with squared units: 1 cm2 = 10−4 m2, not 10−2 m2.

Section 3 of 9Standard form and significant figures

Very large or small numbers are written in standard form, a × 10n with 1 ≤ a < 10. The speed of light is 3.00 × 108 m s−1. Calculator ‘E’ notation (3.00E8) is not acceptable in written answers.

Give final answers to a number of significant figures consistent with the data, usually the same as the least precise value used (commonly 2 or 3). Carry extra digits through intermediate steps and round only at the end. A number such as 0.0450 has three significant figures; the leading zeros do not count.

Section 4 of 9Symbols, equations and language

1
Use the standard symbols: v for velocity, t for time, E for energy, R for resistance, λ for wavelength. Italic for quantities, upright for units.
2
In calculations write the equation first, substitute values with units, then the answer with its unit.
3
Use precise terms: “the current through the resistor” and “the p.d. across it”; “mass” is not “weight”; “heat” is not “temperature”.
4
Write in the past tense, third person, for the method (“the length was measured”).

Section 5 of 9Diagrams and report structure

Circuit diagrams must use standard symbols and ruled lines, with meters in the right place (ammeter in series, voltmeter in parallel).

Diagrams and report structure
Apparatus diagrams should be drawn large, in pencil with a ruler, with labels on every important part and measurements marked,
  • such as the distance being timed.
A report normally has an aim, a variable list (independent, dependent, control), a method, results, analysis, a conclusion and an evaluation.
Presenting results in tables is covered in Presenting and Interpreting Results (1.2.1).

Section 6 of 9Presenting calculations clearly

A well-presented calculation can earn full marks even when the final number is slightly wrong.

Write the equation in symbols, then substitute the numerical values with their units, then give the answer.
What the symbols mean:
For example, kinetic energy of a 0.25 kg trolley moving at 1.6 m s−1: Ek = ½mv2 = ½ × 0.25 × (1.6)2 = 0.32 J.
What the symbols mean: Ek = kinetic energy (J) · m = mass (kg) · v = speed (m s−1)
Put one equals sign per step, align the working down the page, and underline or box the final answer.
When the answer is an estimate the word ‘approximately’ and the symbol ≈ are acceptable, but never use ‘=’ when you have rounded heavily.
Finally, check that the unit is plausible: if a speed comes out in J, something has gone wrong in the working.

Tables of data follow the same rules: headings with symbol and unit, a consistent number of decimal places, and values aligned in columns. Graphs follow the labelling rules too, with a title or caption stating what is plotted. Finally, proofread the report: a missing unit or a misplaced decimal point is easy to overlook and easy to fix.

Section 7 of 9Worked examples

  1. Write 0.000 450 m, 2 350 000 W and 12.5 nA in standard form with base SI units.

  2. A rectangular plate measures 3.2 cm by 4.5 cm. Find its area in m2 to 2 s.f.

  3. A resistor draws 2.5 mA at 6.0 V. Calculate its resistance in standard form with a suitable unit.

Section 8 of 9Key terms

TermMeaning
SI unitsThe internationally agreed system of units based on seven base units.
PrefixA symbol placed before a unit to multiply it by a power of ten.
Standard formA number written as a × 10n where 1 ≤ a < 10.
Significant figureA digit that carries information about the precision of a number.
Base unitOne of the fundamental SI units from which others are derived.
Control variableA quantity deliberately kept constant.

Section 9 of 9Exam technique

1
Forgetting to convert prefixes (mA, cm, g) to base units before substituting.
2
Converting cm2 to m2 by dividing by 100 instead of 10 000.
3
Leaving calculator E-notation in the written answer.
4
Giving a final answer to 6 or 7 significant figures just because the calculator shows them.
5
Drawing diagrams freehand with unlabelled components.
\n