PhysicsUK Connections

Connections.EXPLORE · CONNECT · UNDERSTAND YOUR COURSEOCR A · AS Physics Browse topics →
All apps ↗
55 ideas · 69 connections
Charge flow and electrical power Measuring motion without hiding uncertainty Small length errors can matter greatly in density Stress and pressure share units, but describe different loading Measuring Young modulus accurately Geometry separates resistance from resistivity Why wire diameter matters in resistivity A Planck-constant experiment needs uncertainty analysis Instrument choice sets the measurement limits Charge and current4.1 Energy, power and resistance4.2 Implementing1.1.2 Measurements and uncertainty2.2.1 Kinematics3.1.1 Density and pressure3.2.4 Mechanical properties of matter3.4.2 Resistance4.2.3 Resistivity4.2.4 Photons4.5.1
100%
PHYSICSUK CONNECTIONS
Physics connection

Why wire diameter matters in resistivity

OCR A AS Physics · Two ideas, one explanation

Resistivity is calculated from several measurements. Diameter contributes twice its percentage uncertainty through the cross-sectional area.

ρ = VA/(IL) A = πd²/4

Follow the reasoning

  1. Measure diameter at several positions and directions.
  2. Estimate the uncertainties in voltage, current, length and diameter.
  3. Combine their percentage contributions with the correct powers.
Specification outcomes (4)
  • 4.2.4(a)(i) Define resistivity using R = ρL / A.
  • 4.2.4(a)(ii) Use techniques and procedures to determine the resistivity of a metal.
  • 2.2.1(a) Understand systematic errors (including zero errors) and random errors in measurements.
  • 2.2.1(c) Calculate absolute and percentage uncertainties when data are combined by addition, subtraction, multiplication, division or raising to powers.
Open the official OCR AS specification ↗

H156 v2.0 · May 2026

See it in an exam

A curated collection of checked examples. Coverage is growing; this is not a complete past-paper catalogue.

Put the ideas to work

More practice is on its way

No PhysicsUK question linked yet. New eligible questions appear here as the bank grows.