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55 ideas · 69 connections
Charge flow and electrical power Build a resistor network from Ohm’s law A potential divider uses shared current Changing resistance makes a voltage sensor Geometry separates resistance from resistivity Why wire diameter matters in resistivity Power equations must use the component’s operating point Charge and current4.1 Energy, power and resistance4.2 Measurements and uncertainty2.2.1 Resistance4.2.3 Resistivity4.2.4 Power in circuits4.2.5 Series and parallel circuits4.3.1 Potential dividers4.3.3
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Physics connection

Geometry separates resistance from resistivity

OCR A AS Physics · Two ideas, one explanation

A wire’s resistance depends on its length and area as well as the material. Resistivity describes the material at a specified temperature.

R = ρL/A

Follow the reasoning

  1. Measure or calculate the wire’s cross-sectional area.
  2. Find resistance from voltage and current.
  3. Use the dimensions to calculate resistivity.
Specification outcomes (3)
  • 4.2.4(a)(i) Define resistivity using R = ρL / A.
  • 4.2.3(a) Define resistance using R = V / I and state the unit ohm.
  • 4.2.3(b) State and apply Ohm’s law.
Open the official OCR AS specification ↗

H156 v2.0 · May 2026

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