Practical Skills I: Planning

Revise Practical Skills I: Planning for Physics 3 (IAL) WPH13 (AS Level) — revision notes and instant AI marking.

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Edexcel IAL Physics · Practical Skills I

Planning an Experiment

Big idea: Good experimental planning is just answering four questions properly before you ever touch the apparatus — Every mark in this topic comes from justifying why you chose an instrument or method, not just naming it.

📋 Chapter Summary

Identifying apparatus: every experiment needs the right tool for the quantity you're measuring — rulers, balances, meters, and more precise tools like the micrometer and vernier calipers.
Range & resolution: range = min/max an instrument can read; resolution = smallest increment it can detect. Resolution sets the uncertainty.
Calibration: checking an instrument against a known value (e.g. zero error, ice/steam points) so its readings can be trusted.
Measuring variables: match the instrument's resolution to the size of the quantity — a ruler for cm, calipers for mm, a micrometer for tiny lengths.
Control variables & fair tests: independent variable is deliberately changed, dependent variable is measured, everything else must be held constant.
Repeat readings: improve accuracy/reliability and let you spot anomalies — but aren't always practical (time-dependent or heat-affected experiments).
Health & safety: always name the hazard the specific fix — a bare hazard statement rarely earns the mark.
Data collection: standard form, consistent significant figures, and calculating means (allowed one extra s.f.) turn raw numbers into usable data.
Uncertainty vs. systematic error: uncertainty is the "wobble range" around a reading; a systematic error is a consistent offset from the true value, visible as a graph not passing through the origin.
Wider implications: commercial, legal, ethical, social, economic and environmental factors all shape how science is used and funded.

🔧 1. Identifying Apparatus

Think of apparatus selection as matching a job to the right tool. Just like you wouldn't use a sledgehammer to hang a picture frame, you wouldn't use a metre ruler to measure the diameter of a wire (0.2 mm — you'd barely see it against the ruler's 1 mm markings, let alone read it accurately).

Apparatus falls into two jobs: what you're measuring (the thing being investigated — e.g. an aluminium block) and how you're measuring it (the instruments — thermometer, ammeter, voltmeter, etc).

Quantity	Apparatus
Length	Metre ruler, Vernier calipers, Micrometer screw gauge
Mass	Top-pan balance
Angle	Protractor
Time	Stopwatch
Temperature	Thermometer
Potential difference	Voltmeter
Current	Ammeter
Frequency	Oscilloscope (CRO)

Worked Example: Young Modulus of a Wire

To find Young modulus, you need: diameter of the wire (micrometer — highest resolution for tiny widths), original length (metre ruler), extension (a travelling microscope — designed for tiny length changes), and mass/weight applied (top-pan balance, or a newton-meter to check the masses directly). Notice the pattern: for every measurement, you pick the instrument with the resolution that actually matches the size of the thing you're measuring.

Practice Question

A student wants to measure the diameter of a thin copper wire (approximately 0.5 mm). Which piece of apparatus should they use, and why not a standard 30 cm ruler?