Unit 3 Practical Quick Reference | Flowxiom<\/title>\n<meta name=\"description\" content=\"Unit 3 Practical Quick Reference \u2014 Edexcel A-level Physics WPH. \">\n<link rel=\"canonical\" href=\"https:\/\/flowxiom.com\/edexcel-physics-unit-3-practical-quick-reference\/\">\n\n\n<script>\nMathJax = {\n tex: { inlineMath: [['\\\\(','\\\\)']], displayMath: [['\\\\[','\\\\]']] },\n svg: { fontCache: 'global' }\n};\n<\/script>\n<script async src=\"https:\/\/cdn.jsdelivr.net\/npm\/mathjax@3\/es5\/tex-svg.js\"><\/script>\n\n<style>\n:root{--accent:#2563eb;--warn-bg:#fef9c3;--warn-border:#ca8a04;--formula-bg:#eff6ff;--formula-border:#2563eb;}\nbody{font-family:system-ui,sans-serif;max-width:860px;margin:0 auto;padding:1.5rem;line-height:1.7;color:#1e293b;}\nh1{font-size:2rem;border-bottom:3px solid var(--accent);padding-bottom:.4rem;}\nh2{font-size:1.4rem;color:var(--accent);margin-top:2rem;}\nh3{font-size:1.1rem;margin-top:1.4rem;}\ntable{border-collapse:collapse;width:100%;margin:1rem 0;}\nth,td{border:1px solid #cbd5e1;padding:.5rem .75rem;text-align:left;}\nth{background:#e2e8f0;}\npre,code{background:#f1f5f9;border-radius:4px;}\npre{padding:1rem;overflow-x:auto;}\ncode{padding:.1rem .3rem;font-size:.9em;}\n.seo-warning-box{background:var(--warn-bg);border-left:4px solid var(--warn-border);padding:.75rem 1rem;margin:1rem 0;border-radius:0 6px 6px 0;}\n.seo-note-box{background:#f0fdf4;border-left:4px solid #16a34a;padding:.75rem 1rem;margin:1rem 0;border-radius:0 6px 6px 0;}\nsection.formula-card{background:var(--formula-bg);border:1px solid var(--formula-border);border-radius:8px;padding:1rem 1.25rem;margin:1.5rem 0;}\ndetails{border:1px solid #e2e8f0;border-radius:6px;padding:.5rem 1rem;margin:.75rem 0;}\nsummary{cursor:pointer;font-weight:600;}\n.answer-block{margin-top:.5rem;padding-top:.5rem;border-top:1px solid #e2e8f0;overflow-x:auto;}\n.answer-block p{margin:.25rem 0;}\n.numbered-step{padding-left:1.5rem;position:relative;}\nhr{border:none;border-top:1px solid #e2e8f0;margin:2rem 0;}\n.toc{background:#f8fafc;border:1px solid #e2e8f0;border-radius:8px;padding:1rem 1.5rem;margin-bottom:2rem;}\n.toc h2{margin-top:0;font-size:1.1rem;}\n.toc ul{margin:0;padding-left:1.2rem;}\n.toc a{color:var(--accent);text-decoration:none;}\n.site-footer{margin-top:3rem;padding-top:1rem;border-top:2px solid var(--accent);font-size:.9rem;color:#64748b;}\n<\/style>\n<\/head>\n<body>\n<nav class=\"toc\"><h2>Contents<\/h2><ul>\n <li><a href=\"#instrument-precision\">Instrument Precision<\/a><\/li>\n <li><a href=\"#10-core-practicals\">10 Core Practicals<\/a><\/li>\n <li><a href=\"#general-graph-rules\">General Graph Rules<\/a><\/li>\n <li><a href=\"#experimental-design-framework-6mark-question\">Experimental Design Framework (6-mark question)<\/a><\/li>\n <li><a href=\"#standard-sentence-bank\">Standard Sentence Bank<\/a><\/li>\n <li><a href=\"#wph13-exam-format-guide\">WPH13 Exam Format Guide<\/a><\/li>\n<\/ul><\/nav>\n<h1>Unit 3 Practical Quick Reference<\/h1>\n<p><strong>Free resource by <a href=\"https:\/\/flowxiom.com\">Flowxiom<\/a> \u2014 Edexcel A-level Physics<\/strong><\/p>\n<p><em>Not everything. Just what’s on the paper. High-frequency topics only \u2014 covering ~80% of exam marks.<\/em><\/p>\n<p>Edexcel A-level Physics | AS Core Practicals | WPH13<\/p>\n<hr>\n<h2 id=\"instrument-precision\">Instrument Precision<\/h2>\n<table>\n<thead><tr><th>Instrument<\/th><th>Precision<\/th><th>Used for<\/th><\/tr><\/thead>\n<tr><td>Metre rule<\/td><td>1 mm<\/td><td>Length, pendulum length, wire length<\/td><\/tr>\n<tr><td>Vernier calliper<\/td><td>0.1 mm<\/td><td>Tube diameter, small lengths<\/td><\/tr>\n<tr><td>Micrometer<\/td><td>0.01 mm<\/td><td>Wire diameter, thin metal wire<\/td><\/tr>\n<tr><td>Stopwatch<\/td><td>0.01 s (but human reaction time ~0.2 s)<\/td><td>Longer time intervals<\/td><\/tr>\n<tr><td>Light gate<\/td><td>Very high<\/td><td>Short time intervals, instantaneous speed<\/td><\/tr>\n<\/table>\n\n<div class=\"seo-warning-box\">\n<p>\u26a0\ufe0f Wire diameter <strong>must<\/strong> be measured with a micrometer \u2014 Vernier calliper is not precise enough.<\/p>\n<\/div>\n<hr>\n<h2 id=\"10-core-practicals\">10 Core Practicals<\/h2>\n<h3 id=\"practical-1-determination-of-acceleration-of-free-fall-latexblock0xend\">Practical 1: Determination of Acceleration of Free Fall \\(g\\)<\/h3>\n<p><strong>Formula:<\/strong> \\(s = \\frac{1}{2}gt^2\\)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Electromagnet releases ball and starts timer simultaneously \u2014 eliminates reaction time error<\/li>\n<li>Vary drop height \\(h\\); plot \\(h\\) vs \\(t^2\\) graph; gradient \\(= g\/2\\)<\/li>\n<\/ul>\n<p><strong>Sources of error:<\/strong><\/p>\n<ul>\n<li>Residual magnetism causes time delay on release<\/li>\n<li>Air currents<\/li>\n<li>If using pendulum: keep amplitude \\(< 10\u00b0\\); time 20 complete oscillations then divide<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-2-determination-of-young-modulus\">Practical 2: Determination of Young Modulus<\/h3>\n<p><strong>Formula:<\/strong> \\(E = \\dfrac{FL}{A\\Delta L}\\)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Use the longest possible wire \u2014 increases extension \\(\\Delta L\\), reduces percentage uncertainty<\/li>\n<li>Measure wire diameter with micrometer at 3 different positions and average<\/li>\n<li>Plot \\(F\\) vs \\(\\Delta L\\) graph; gradient \\(= EA\/L\\)<\/li>\n<\/ul>\n<p><strong>Safety:<\/strong> Safety goggles must be worn \u2014 snapping wire can cause injury.<\/p>\n<hr>\n<h3 id=\"practical-3-determination-of-resistivity-of-a-metal-wire\">Practical 3: Determination of Resistivity of a Metal Wire<\/h3>\n<p><strong>Formula:<\/strong> \\(R = \\rho\\dfrac{l}{A}\\)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Vary wire length \\(l\\) and measure corresponding resistance \\(R\\)<\/li>\n<li>Plot \\(R\\) vs \\(l\\) graph; gradient \\(= \\rho\/A\\)<\/li>\n<li>Switch off immediately after each reading \u2014 prevents wire heating and resistance change<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-4-determination-of-emf-and-internal-resistance\">Practical 4: Determination of E.M.F. and Internal Resistance<\/h3>\n<p><strong>Formula:<\/strong> \\(V = \\varepsilon – Ir\\) (i.e. \\(V = -rI + \\varepsilon\\) \u2014 linear form for graph)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Use a variable resistor (rheostat) to vary current \\(I\\)<\/li>\n<li>Plot \\(V\\) vs \\(I\\) graph:<\/li>\n<\/ul>\n<p>– y-intercept \\(= \\varepsilon\\) (e.m.f.)<\/p>\n<p>– magnitude of gradient \\(= r\\) (internal resistance)<\/p>\n<hr>\n<h3 id=\"practical-5-investigation-of-ntc-thermistor-characteristics\">Practical 5: Investigation of NTC Thermistor Characteristics<\/h3>\n<p><strong>Observation:<\/strong> Temperature increases \u2192 resistance decreases (non-linear)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Heat using a water bath; record resistance at different temperatures<\/li>\n<li>Plot \\(R\\) vs \\(T\\) (curve), or \\(\\ln R\\) vs \\(1\/T\\) (straight line)<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-6-determination-of-viscosity-of-a-liquid\">Practical 6: Determination of Viscosity of a Liquid<\/h3>\n<p><strong>Formula:<\/strong> \\(F_{drag} = 6\\pi\\eta rv\\) (Stokes’ Law)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>At terminal velocity: weight = upthrust + drag force<\/li>\n<li>Use light gates at different depths to confirm terminal velocity has been reached<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-7-determination-of-refractive-index\">Practical 7: Determination of Refractive Index<\/h3>\n<p><strong>Formula:<\/strong> \\(n = \\dfrac{\\sin i}{\\sin r}\\)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Use pins to mark the incident and refracted ray paths<\/li>\n<li>Vary angle of incidence \\(i\\) from 10\u00b0 to 70\u00b0; record angle of refraction \\(r\\)<\/li>\n<li>Plot \\(\\sin i\\) vs \\(\\sin r\\) graph; gradient \\(= n\\)<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-8-investigation-of-stationary-waves-on-a-string\">Practical 8: Investigation of Stationary Waves on a String<\/h3>\n<p><strong>Formula:<\/strong> \\(f = \\dfrac{1}{2L}\\sqrt{\\dfrac{T}{\\mu}}\\), fundamental: \\(\\lambda = 2L\\)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Adjust frequency until first harmonic (one antinode) appears<\/li>\n<li>Vary string length or tension; record resonant frequencies<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-9-finding-the-centre-of-gravity-plumb-line-method\">Practical 9: Finding the Centre of Gravity \u2014 Plumb Line Method<\/h3>\n<p class=\"numbered-step\">Hang the irregular lamina from one point; draw a vertical line through the pivot<\/p>\n<p class=\"numbered-step\">Hang from a different point; draw another vertical line<\/p>\n<p class=\"numbered-step\">Intersection of the two lines = centre of gravity<\/p>\n<hr>\n<h3 id=\"practical-10-general-error-analysis\">Practical 10: General Error Analysis<\/h3>\n<p>See: <strong>01 Uncertainty Quick Reference<\/strong><\/p>\n<hr>\n<h2 id=\"general-graph-rules\">General Graph Rules<\/h2>\n<h3 id=\"table-format\">Table Format<\/h3>\n<pre><code>Correct: Length l \/ m Resistance R \/ \u03a9\nIncorrect: Length l (m) Resistance R (\u03a9)<\/code><\/pre>\n<p>Header format: <em>quantity symbol \/ unit<\/em><\/p>\n<h3 id=\"graph-drawing-rules\">Graph Drawing Rules<\/h3>\n<ul>\n<li>Axis label: <strong>quantity \/ unit<\/strong> (e.g. <code>t\u00b2 \/ s\u00b2<\/code>)<\/li>\n<li>Plot data points with \u00d7 or \u2295<\/li>\n<li>Best-fit line: straight; points scatter evenly either side; do not force through every point<\/li>\n<li>Gradient: use two points on the line as far apart as possible (large triangle)<\/li>\n<\/ul>\n<h3 id=\"linearisation\">Linearisation<\/h3>\n<table>\n<thead><tr><th>Original<\/th><th>Graph to plot<\/th><th>Gradient<\/th><th>Intercept<\/th><\/tr><\/thead>\n<tr><td>\\(y = ax^2\\)<\/td><td>\\(y\\) vs \\(x^2\\)<\/td><td>\\(a\\)<\/td><td>0<\/td><\/tr>\n<tr><td>\\(y = ax^n\\)<\/td><td>\\(\\lg y\\) vs \\(\\lg x\\)<\/td><td>\\(n\\)<\/td><td>\\(\\lg a\\)<\/td><\/tr>\n<tr><td>\\(T = 2\\pi\\sqrt{L\/g}\\)<\/td><td>\\(T^2\\) vs \\(L\\)<\/td><td>\\(4\\pi^2\/g\\)<\/td><td>0<\/td><\/tr>\n<tr><td>\\(V = \\varepsilon – Ir\\)<\/td><td>\\(V\\) vs \\(I\\)<\/td><td>\\(-r\\)<\/td><td>\\(\\varepsilon\\)<\/td><\/tr>\n<\/table>\n\n<hr>\n<h2 id=\"experimental-design-framework-6mark-question\">Experimental Design Framework (6-mark question)<\/h2>\n<p>For “design an experiment to measure X”, answer in this order:<\/p>\n<p class=\"numbered-step\"><strong>Diagram<\/strong> \u2014 label all apparatus<\/p>\n<p class=\"numbered-step\"><strong>Variables<\/strong>: independent, dependent, control variables<\/p>\n<p class=\"numbered-step\"><strong>Procedure<\/strong>: how to change the independent variable; how to measure the dependent variable<\/p>\n<p class=\"numbered-step\"><strong>Data analysis<\/strong>: state which graph to plot and what the gradient\/intercept gives<\/p>\n<p class=\"numbered-step\"><strong>Reducing uncertainty<\/strong>: repeat measurements and average; use more precise instruments<\/p>\n<p class=\"numbered-step\"><strong>Safety<\/strong>: at least one safety precaution<\/p>\n<hr>\n<h2 id=\"standard-sentence-bank\">Standard Sentence Bank<\/h2>\n<p><strong>Sources of error:<\/strong><\/p>\n<ul>\n<li>Parallax error when taking readings<\/li>\n<li>Human reaction time causes timing error<\/li>\n<li>Wire heats up during current flow, changing resistance<\/li>\n<li>Air currents affect pendulum motion<\/li>\n<\/ul>\n<p><strong>Improvements:<\/strong><\/p>\n<ul>\n<li>Use a light gate instead of a stopwatch (eliminates reaction time error)<\/li>\n<li>Time 20 oscillations and divide by 20 (reduces percentage uncertainty)<\/li>\n<li>Switch off circuit immediately after each reading (prevents heating)<\/li>\n<li>Measure at multiple positions and average (reduces random error)<\/li>\n<\/ul>\n<hr>\n<h2 id=\"wph13-exam-format-guide\">WPH13 Exam Format Guide<\/h2>\n<h3 id=\"mark-allocation\">Mark Allocation<\/h3>\n<p>WPH13 = 40 marks, approximately 2 hours, two large practical questions.<\/p>\n<table>\n<thead><tr><th>Section<\/th><th>Typical marks<\/th><th>Common cause of mark loss<\/th><\/tr><\/thead>\n<tr><td>Readings (with uncertainty)<\/td><td>4\u20136<\/td><td>Insufficient precision \/ missing units \/ no uncertainty<\/td><\/tr>\n<tr><td>Data table<\/td><td>2\u20133<\/td><td>Wrong header format \/ inconsistent significant figures<\/td><\/tr>\n<tr><td>Graph<\/td><td>6\u20138<\/td><td>No units on axes \/ data doesn’t fill graph \/ forced through every point<\/td><\/tr>\n<tr><td>Gradient<\/td><td>3\u20134<\/td><td>Triangle too small \/ used data points not line points<\/td><\/tr>\n<tr><td>Conclusion<\/td><td>3\u20135<\/td><td>Stated result without linking to equation<\/td><\/tr>\n<\/table>\n\n<h3 id=\"reading-standards\">Reading Standards<\/h3>\n<ul>\n<li>Millimetre rule: read to <strong>1 mm<\/strong>, estimate to 0.5 mm<\/li>\n<li>Vernier calliper: read to <strong>0.1 mm<\/strong><\/li>\n<li>Micrometer: read to <strong>0.01 mm<\/strong><\/li>\n<li>Stopwatch: read to <strong>0.01 s<\/strong> (but human reaction time ~0.2 s)<\/li>\n<li>Every reading must include absolute uncertainty: \\((34.5 \\pm 0.5)\\ \\text{mm}\\)<\/li>\n<\/ul>\n<h3 id=\"table-format-rules\">Table Format Rules<\/h3>\n<pre><code>Correct: L \/ m T\u00b2 \/ s\u00b2 ln(V \/ V)\nIncorrect: L(m) T\u00b2(s\u00b2) lnV<\/code><\/pre>\n<ul>\n<li>Decimal places must be consistent within a column<\/li>\n<li>Uncertainty in \\(T^2\\): \\(\\dfrac{\\Delta T^2}{T^2} = 2\\dfrac{\\Delta T}{T}\\)<\/li>\n<\/ul>\n<h3 id=\"graph-rules\">Graph Rules<\/h3>\n<p class=\"numbered-step\">Uniform scale; label as “quantity \/ unit”<\/p>\n<p class=\"numbered-step\">Data must occupy > 50% of grid<\/p>\n<p class=\"numbered-step\">Best-fit line: points scatter evenly either side<\/p>\n<p class=\"numbered-step\">Gradient: use points on the line (not data points); triangle must be large<\/p>\n<h3 id=\"standard-improvement-phrases\">Standard Improvement Phrases<\/h3>\n<table>\n<thead><tr><th>Problem<\/th><th>Model answer<\/th><\/tr><\/thead>\n<tr><td>Reduce timing error<\/td><td>Time 20 oscillations; divide by 20 to reduce percentage uncertainty<\/td><\/tr>\n<tr><td>Reduce parallax<\/td><td>Read at eye level perpendicular to scale; use Vernier calliper or light gate<\/td><\/tr>\n<tr><td>Reduce systematic error<\/td><td>Zero the instrument; use gradient method rather than single measurement<\/td><\/tr>\n<tr><td>Detect terminal velocity<\/td><td>Use light gates at different depths until speed stops changing<\/td><\/tr>\n<tr><td>Why repeat and average<\/td><td>Reduces random error and improves reliability<\/td><\/tr>\n<\/table>\n\n<hr>\n<p><em>Want more? Visit <a href=\"https:\/\/flowxiom.com\">flowxiom.com<\/a><\/em><\/p>\n<footer class=\"site-footer\">\n <p>Free resource by <a href=\"https:\/\/flowxiom.com\">Flowxiom<\/a> \u2014 Edexcel A-level Physics<br>\n High-frequency topics only, covering ~80% of exam marks.<\/p>\n<\/footer>\n<\/body>\n<\/html>\n\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>This is a practical “handbook” for the Unit 3 exam. It teaches you how to act like a scientist in the lab and on paper. Key topics include:<\/p>\n<p>Instrument Guide: When to use a micrometer versus a Vernier calliper.<\/p>\n<p>The 10 Practicals: Step-by-step methods for all mandatory experiments.<\/p>\n<p>Graph Rules: How to label axes, draw best-fit lines, and calculate gradients correctly.<\/p>\n<p>6-Mark Secrets: A simple framework (Diagram, Variables, Procedure, Analysis, Safety) to help you ace long-answer questions.<\/p>\n<p>Error Analysis: Standard phrases to explain how to reduce parallax and random errors.<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-42","post","type-post","status-publish","format-standard","hentry","category-exam-sprint-pack-physics-exam-sprint-pack"],"_links":{"self":[{"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/posts\/42","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/comments?post=42"}],"version-history":[{"count":2,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/posts\/42\/revisions"}],"predecessor-version":[{"id":44,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/posts\/42\/revisions\/44"}],"wp:attachment":[{"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/media?parent=42"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/categories?post=42"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/tags?post=42"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}

{"id":42,"date":"2026-04-17T16:18:08","date_gmt":"2026-04-17T16:18:08","guid":{"rendered":"https:\/\/flowxiom.com\/?p=42"},"modified":"2026-04-17T16:19:30","modified_gmt":"2026-04-17T16:19:30","slug":"unit-3-practical-quick-reference","status":"publish","type":"post","link":"https:\/\/flowxiom.com\/index.php\/2026\/04\/17\/unit-3-practical-quick-reference\/","title":{"rendered":"Unit 3 Practical Quick Reference"},"content":{"rendered":"\n\n\n\n\n\nUnit 3 Practical Quick Reference | Flowxiom<\/title>\n<meta name=\"description\" content=\"Unit 3 Practical Quick Reference \u2014 Edexcel A-level Physics WPH. \">\n<link rel=\"canonical\" href=\"https:\/\/flowxiom.com\/edexcel-physics-unit-3-practical-quick-reference\/\">\n\n\n<script>\nMathJax = {\n tex: { inlineMath: [['\\\\(','\\\\)']], displayMath: [['\\\\[','\\\\]']] },\n svg: { fontCache: 'global' }\n};\n<\/script>\n<script async src=\"https:\/\/cdn.jsdelivr.net\/npm\/mathjax@3\/es5\/tex-svg.js\"><\/script>\n\n<style>\n:root{--accent:#2563eb;--warn-bg:#fef9c3;--warn-border:#ca8a04;--formula-bg:#eff6ff;--formula-border:#2563eb;}\nbody{font-family:system-ui,sans-serif;max-width:860px;margin:0 auto;padding:1.5rem;line-height:1.7;color:#1e293b;}\nh1{font-size:2rem;border-bottom:3px solid var(--accent);padding-bottom:.4rem;}\nh2{font-size:1.4rem;color:var(--accent);margin-top:2rem;}\nh3{font-size:1.1rem;margin-top:1.4rem;}\ntable{border-collapse:collapse;width:100%;margin:1rem 0;}\nth,td{border:1px solid #cbd5e1;padding:.5rem .75rem;text-align:left;}\nth{background:#e2e8f0;}\npre,code{background:#f1f5f9;border-radius:4px;}\npre{padding:1rem;overflow-x:auto;}\ncode{padding:.1rem .3rem;font-size:.9em;}\n.seo-warning-box{background:var(--warn-bg);border-left:4px solid var(--warn-border);padding:.75rem 1rem;margin:1rem 0;border-radius:0 6px 6px 0;}\n.seo-note-box{background:#f0fdf4;border-left:4px solid #16a34a;padding:.75rem 1rem;margin:1rem 0;border-radius:0 6px 6px 0;}\nsection.formula-card{background:var(--formula-bg);border:1px solid var(--formula-border);border-radius:8px;padding:1rem 1.25rem;margin:1.5rem 0;}\ndetails{border:1px solid #e2e8f0;border-radius:6px;padding:.5rem 1rem;margin:.75rem 0;}\nsummary{cursor:pointer;font-weight:600;}\n.answer-block{margin-top:.5rem;padding-top:.5rem;border-top:1px solid #e2e8f0;overflow-x:auto;}\n.answer-block p{margin:.25rem 0;}\n.numbered-step{padding-left:1.5rem;position:relative;}\nhr{border:none;border-top:1px solid #e2e8f0;margin:2rem 0;}\n.toc{background:#f8fafc;border:1px solid #e2e8f0;border-radius:8px;padding:1rem 1.5rem;margin-bottom:2rem;}\n.toc h2{margin-top:0;font-size:1.1rem;}\n.toc ul{margin:0;padding-left:1.2rem;}\n.toc a{color:var(--accent);text-decoration:none;}\n.site-footer{margin-top:3rem;padding-top:1rem;border-top:2px solid var(--accent);font-size:.9rem;color:#64748b;}\n<\/style>\n<\/head>\n<body>\n<nav class=\"toc\"><h2>Contents<\/h2><ul>\n <li><a href=\"#instrument-precision\">Instrument Precision<\/a><\/li>\n <li><a href=\"#10-core-practicals\">10 Core Practicals<\/a><\/li>\n <li><a href=\"#general-graph-rules\">General Graph Rules<\/a><\/li>\n <li><a href=\"#experimental-design-framework-6mark-question\">Experimental Design Framework (6-mark question)<\/a><\/li>\n <li><a href=\"#standard-sentence-bank\">Standard Sentence Bank<\/a><\/li>\n <li><a href=\"#wph13-exam-format-guide\">WPH13 Exam Format Guide<\/a><\/li>\n<\/ul><\/nav>\n<h1>Unit 3 Practical Quick Reference<\/h1>\n<p><strong>Free resource by <a href=\"https:\/\/flowxiom.com\">Flowxiom<\/a> \u2014 Edexcel A-level Physics<\/strong><\/p>\n<p><em>Not everything. Just what’s on the paper. High-frequency topics only \u2014 covering ~80% of exam marks.<\/em><\/p>\n<p>Edexcel A-level Physics | AS Core Practicals | WPH13<\/p>\n<hr>\n<h2 id=\"instrument-precision\">Instrument Precision<\/h2>\n<table>\n<thead><tr><th>Instrument<\/th><th>Precision<\/th><th>Used for<\/th><\/tr><\/thead>\n<tr><td>Metre rule<\/td><td>1 mm<\/td><td>Length, pendulum length, wire length<\/td><\/tr>\n<tr><td>Vernier calliper<\/td><td>0.1 mm<\/td><td>Tube diameter, small lengths<\/td><\/tr>\n<tr><td>Micrometer<\/td><td>0.01 mm<\/td><td>Wire diameter, thin metal wire<\/td><\/tr>\n<tr><td>Stopwatch<\/td><td>0.01 s (but human reaction time ~0.2 s)<\/td><td>Longer time intervals<\/td><\/tr>\n<tr><td>Light gate<\/td><td>Very high<\/td><td>Short time intervals, instantaneous speed<\/td><\/tr>\n<\/table>\n\n<div class=\"seo-warning-box\">\n<p>\u26a0\ufe0f Wire diameter <strong>must<\/strong> be measured with a micrometer \u2014 Vernier calliper is not precise enough.<\/p>\n<\/div>\n<hr>\n<h2 id=\"10-core-practicals\">10 Core Practicals<\/h2>\n<h3 id=\"practical-1-determination-of-acceleration-of-free-fall-latexblock0xend\">Practical 1: Determination of Acceleration of Free Fall \\(g\\)<\/h3>\n<p><strong>Formula:<\/strong> \\(s = \\frac{1}{2}gt^2\\)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Electromagnet releases ball and starts timer simultaneously \u2014 eliminates reaction time error<\/li>\n<li>Vary drop height \\(h\\); plot \\(h\\) vs \\(t^2\\) graph; gradient \\(= g\/2\\)<\/li>\n<\/ul>\n<p><strong>Sources of error:<\/strong><\/p>\n<ul>\n<li>Residual magnetism causes time delay on release<\/li>\n<li>Air currents<\/li>\n<li>If using pendulum: keep amplitude \\(< 10\u00b0\\); time 20 complete oscillations then divide<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-2-determination-of-young-modulus\">Practical 2: Determination of Young Modulus<\/h3>\n<p><strong>Formula:<\/strong> \\(E = \\dfrac{FL}{A\\Delta L}\\)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Use the longest possible wire \u2014 increases extension \\(\\Delta L\\), reduces percentage uncertainty<\/li>\n<li>Measure wire diameter with micrometer at 3 different positions and average<\/li>\n<li>Plot \\(F\\) vs \\(\\Delta L\\) graph; gradient \\(= EA\/L\\)<\/li>\n<\/ul>\n<p><strong>Safety:<\/strong> Safety goggles must be worn \u2014 snapping wire can cause injury.<\/p>\n<hr>\n<h3 id=\"practical-3-determination-of-resistivity-of-a-metal-wire\">Practical 3: Determination of Resistivity of a Metal Wire<\/h3>\n<p><strong>Formula:<\/strong> \\(R = \\rho\\dfrac{l}{A}\\)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Vary wire length \\(l\\) and measure corresponding resistance \\(R\\)<\/li>\n<li>Plot \\(R\\) vs \\(l\\) graph; gradient \\(= \\rho\/A\\)<\/li>\n<li>Switch off immediately after each reading \u2014 prevents wire heating and resistance change<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-4-determination-of-emf-and-internal-resistance\">Practical 4: Determination of E.M.F. and Internal Resistance<\/h3>\n<p><strong>Formula:<\/strong> \\(V = \\varepsilon – Ir\\) (i.e. \\(V = -rI + \\varepsilon\\) \u2014 linear form for graph)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Use a variable resistor (rheostat) to vary current \\(I\\)<\/li>\n<li>Plot \\(V\\) vs \\(I\\) graph:<\/li>\n<\/ul>\n<p>– y-intercept \\(= \\varepsilon\\) (e.m.f.)<\/p>\n<p>– magnitude of gradient \\(= r\\) (internal resistance)<\/p>\n<hr>\n<h3 id=\"practical-5-investigation-of-ntc-thermistor-characteristics\">Practical 5: Investigation of NTC Thermistor Characteristics<\/h3>\n<p><strong>Observation:<\/strong> Temperature increases \u2192 resistance decreases (non-linear)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Heat using a water bath; record resistance at different temperatures<\/li>\n<li>Plot \\(R\\) vs \\(T\\) (curve), or \\(\\ln R\\) vs \\(1\/T\\) (straight line)<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-6-determination-of-viscosity-of-a-liquid\">Practical 6: Determination of Viscosity of a Liquid<\/h3>\n<p><strong>Formula:<\/strong> \\(F_{drag} = 6\\pi\\eta rv\\) (Stokes’ Law)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>At terminal velocity: weight = upthrust + drag force<\/li>\n<li>Use light gates at different depths to confirm terminal velocity has been reached<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-7-determination-of-refractive-index\">Practical 7: Determination of Refractive Index<\/h3>\n<p><strong>Formula:<\/strong> \\(n = \\dfrac{\\sin i}{\\sin r}\\)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Use pins to mark the incident and refracted ray paths<\/li>\n<li>Vary angle of incidence \\(i\\) from 10\u00b0 to 70\u00b0; record angle of refraction \\(r\\)<\/li>\n<li>Plot \\(\\sin i\\) vs \\(\\sin r\\) graph; gradient \\(= n\\)<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-8-investigation-of-stationary-waves-on-a-string\">Practical 8: Investigation of Stationary Waves on a String<\/h3>\n<p><strong>Formula:<\/strong> \\(f = \\dfrac{1}{2L}\\sqrt{\\dfrac{T}{\\mu}}\\), fundamental: \\(\\lambda = 2L\\)<\/p>\n<p><strong>Key operations:<\/strong><\/p>\n<ul>\n<li>Adjust frequency until first harmonic (one antinode) appears<\/li>\n<li>Vary string length or tension; record resonant frequencies<\/li>\n<\/ul>\n<hr>\n<h3 id=\"practical-9-finding-the-centre-of-gravity-plumb-line-method\">Practical 9: Finding the Centre of Gravity \u2014 Plumb Line Method<\/h3>\n<p class=\"numbered-step\">Hang the irregular lamina from one point; draw a vertical line through the pivot<\/p>\n<p class=\"numbered-step\">Hang from a different point; draw another vertical line<\/p>\n<p class=\"numbered-step\">Intersection of the two lines = centre of gravity<\/p>\n<hr>\n<h3 id=\"practical-10-general-error-analysis\">Practical 10: General Error Analysis<\/h3>\n<p>See: <strong>01 Uncertainty Quick Reference<\/strong><\/p>\n<hr>\n<h2 id=\"general-graph-rules\">General Graph Rules<\/h2>\n<h3 id=\"table-format\">Table Format<\/h3>\n<pre><code>Correct: Length l \/ m Resistance R \/ \u03a9\nIncorrect: Length l (m) Resistance R (\u03a9)<\/code><\/pre>\n<p>Header format: <em>quantity symbol \/ unit<\/em><\/p>\n<h3 id=\"graph-drawing-rules\">Graph Drawing Rules<\/h3>\n<ul>\n<li>Axis label: <strong>quantity \/ unit<\/strong> (e.g. <code>t\u00b2 \/ s\u00b2<\/code>)<\/li>\n<li>Plot data points with \u00d7 or \u2295<\/li>\n<li>Best-fit line: straight; points scatter evenly either side; do not force through every point<\/li>\n<li>Gradient: use two points on the line as far apart as possible (large triangle)<\/li>\n<\/ul>\n<h3 id=\"linearisation\">Linearisation<\/h3>\n<table>\n<thead><tr><th>Original<\/th><th>Graph to plot<\/th><th>Gradient<\/th><th>Intercept<\/th><\/tr><\/thead>\n<tr><td>\\(y = ax^2\\)<\/td><td>\\(y\\) vs \\(x^2\\)<\/td><td>\\(a\\)<\/td><td>0<\/td><\/tr>\n<tr><td>\\(y = ax^n\\)<\/td><td>\\(\\lg y\\) vs \\(\\lg x\\)<\/td><td>\\(n\\)<\/td><td>\\(\\lg a\\)<\/td><\/tr>\n<tr><td>\\(T = 2\\pi\\sqrt{L\/g}\\)<\/td><td>\\(T^2\\) vs \\(L\\)<\/td><td>\\(4\\pi^2\/g\\)<\/td><td>0<\/td><\/tr>\n<tr><td>\\(V = \\varepsilon – Ir\\)<\/td><td>\\(V\\) vs \\(I\\)<\/td><td>\\(-r\\)<\/td><td>\\(\\varepsilon\\)<\/td><\/tr>\n<\/table>\n\n<hr>\n<h2 id=\"experimental-design-framework-6mark-question\">Experimental Design Framework (6-mark question)<\/h2>\n<p>For “design an experiment to measure X”, answer in this order:<\/p>\n<p class=\"numbered-step\"><strong>Diagram<\/strong> \u2014 label all apparatus<\/p>\n<p class=\"numbered-step\"><strong>Variables<\/strong>: independent, dependent, control variables<\/p>\n<p class=\"numbered-step\"><strong>Procedure<\/strong>: how to change the independent variable; how to measure the dependent variable<\/p>\n<p class=\"numbered-step\"><strong>Data analysis<\/strong>: state which graph to plot and what the gradient\/intercept gives<\/p>\n<p class=\"numbered-step\"><strong>Reducing uncertainty<\/strong>: repeat measurements and average; use more precise instruments<\/p>\n<p class=\"numbered-step\"><strong>Safety<\/strong>: at least one safety precaution<\/p>\n<hr>\n<h2 id=\"standard-sentence-bank\">Standard Sentence Bank<\/h2>\n<p><strong>Sources of error:<\/strong><\/p>\n<ul>\n<li>Parallax error when taking readings<\/li>\n<li>Human reaction time causes timing error<\/li>\n<li>Wire heats up during current flow, changing resistance<\/li>\n<li>Air currents affect pendulum motion<\/li>\n<\/ul>\n<p><strong>Improvements:<\/strong><\/p>\n<ul>\n<li>Use a light gate instead of a stopwatch (eliminates reaction time error)<\/li>\n<li>Time 20 oscillations and divide by 20 (reduces percentage uncertainty)<\/li>\n<li>Switch off circuit immediately after each reading (prevents heating)<\/li>\n<li>Measure at multiple positions and average (reduces random error)<\/li>\n<\/ul>\n<hr>\n<h2 id=\"wph13-exam-format-guide\">WPH13 Exam Format Guide<\/h2>\n<h3 id=\"mark-allocation\">Mark Allocation<\/h3>\n<p>WPH13 = 40 marks, approximately 2 hours, two large practical questions.<\/p>\n<table>\n<thead><tr><th>Section<\/th><th>Typical marks<\/th><th>Common cause of mark loss<\/th><\/tr><\/thead>\n<tr><td>Readings (with uncertainty)<\/td><td>4\u20136<\/td><td>Insufficient precision \/ missing units \/ no uncertainty<\/td><\/tr>\n<tr><td>Data table<\/td><td>2\u20133<\/td><td>Wrong header format \/ inconsistent significant figures<\/td><\/tr>\n<tr><td>Graph<\/td><td>6\u20138<\/td><td>No units on axes \/ data doesn’t fill graph \/ forced through every point<\/td><\/tr>\n<tr><td>Gradient<\/td><td>3\u20134<\/td><td>Triangle too small \/ used data points not line points<\/td><\/tr>\n<tr><td>Conclusion<\/td><td>3\u20135<\/td><td>Stated result without linking to equation<\/td><\/tr>\n<\/table>\n\n<h3 id=\"reading-standards\">Reading Standards<\/h3>\n<ul>\n<li>Millimetre rule: read to <strong>1 mm<\/strong>, estimate to 0.5 mm<\/li>\n<li>Vernier calliper: read to <strong>0.1 mm<\/strong><\/li>\n<li>Micrometer: read to <strong>0.01 mm<\/strong><\/li>\n<li>Stopwatch: read to <strong>0.01 s<\/strong> (but human reaction time ~0.2 s)<\/li>\n<li>Every reading must include absolute uncertainty: \\((34.5 \\pm 0.5)\\ \\text{mm}\\)<\/li>\n<\/ul>\n<h3 id=\"table-format-rules\">Table Format Rules<\/h3>\n<pre><code>Correct: L \/ m T\u00b2 \/ s\u00b2 ln(V \/ V)\nIncorrect: L(m) T\u00b2(s\u00b2) lnV<\/code><\/pre>\n<ul>\n<li>Decimal places must be consistent within a column<\/li>\n<li>Uncertainty in \\(T^2\\): \\(\\dfrac{\\Delta T^2}{T^2} = 2\\dfrac{\\Delta T}{T}\\)<\/li>\n<\/ul>\n<h3 id=\"graph-rules\">Graph Rules<\/h3>\n<p class=\"numbered-step\">Uniform scale; label as “quantity \/ unit”<\/p>\n<p class=\"numbered-step\">Data must occupy > 50% of grid<\/p>\n<p class=\"numbered-step\">Best-fit line: points scatter evenly either side<\/p>\n<p class=\"numbered-step\">Gradient: use points on the line (not data points); triangle must be large<\/p>\n<h3 id=\"standard-improvement-phrases\">Standard Improvement Phrases<\/h3>\n<table>\n<thead><tr><th>Problem<\/th><th>Model answer<\/th><\/tr><\/thead>\n<tr><td>Reduce timing error<\/td><td>Time 20 oscillations; divide by 20 to reduce percentage uncertainty<\/td><\/tr>\n<tr><td>Reduce parallax<\/td><td>Read at eye level perpendicular to scale; use Vernier calliper or light gate<\/td><\/tr>\n<tr><td>Reduce systematic error<\/td><td>Zero the instrument; use gradient method rather than single measurement<\/td><\/tr>\n<tr><td>Detect terminal velocity<\/td><td>Use light gates at different depths until speed stops changing<\/td><\/tr>\n<tr><td>Why repeat and average<\/td><td>Reduces random error and improves reliability<\/td><\/tr>\n<\/table>\n\n<hr>\n<p><em>Want more? Visit <a href=\"https:\/\/flowxiom.com\">flowxiom.com<\/a><\/em><\/p>\n<footer class=\"site-footer\">\n <p>Free resource by <a href=\"https:\/\/flowxiom.com\">Flowxiom<\/a> \u2014 Edexcel A-level Physics<br>\n High-frequency topics only, covering ~80% of exam marks.<\/p>\n<\/footer>\n<\/body>\n<\/html>\n\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>This is a practical “handbook” for the Unit 3 exam. It teaches you how to act like a scientist in the lab and on paper. Key topics include:<\/p>\n<p>Instrument Guide: When to use a micrometer versus a Vernier calliper.<\/p>\n<p>The 10 Practicals: Step-by-step methods for all mandatory experiments.<\/p>\n<p>Graph Rules: How to label axes, draw best-fit lines, and calculate gradients correctly.<\/p>\n<p>6-Mark Secrets: A simple framework (Diagram, Variables, Procedure, Analysis, Safety) to help you ace long-answer questions.<\/p>\n<p>Error Analysis: Standard phrases to explain how to reduce parallax and random errors.<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-42","post","type-post","status-publish","format-standard","hentry","category-exam-sprint-pack-physics-exam-sprint-pack"],"_links":{"self":[{"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/posts\/42","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/comments?post=42"}],"version-history":[{"count":2,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/posts\/42\/revisions"}],"predecessor-version":[{"id":44,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/posts\/42\/revisions\/44"}],"wp:attachment":[{"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/media?parent=42"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/categories?post=42"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/flowxiom.com\/index.php\/wp-json\/wp\/v2\/tags?post=42"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}