This document provides an overview of electrical conductivity and resistance in materials. It explains that good conductors allow electrons to flow easily between atoms, while insulators have a high resistance and impede electron flow. Resistance is measured in ohms and depends on a material's resistivity, length, and cross-sectional area. Conductivity is the inverse of resistivity and relates to how well a material conducts electricity. The document suggests measuring resistance of wires with varying lengths and thicknesses to calculate resistivity and conductivity.

1. Conducting Very Well - Conducting Very Badly A guide to electrical properties

2. Good Conductor or Insulator? Does it allows electrical current to flow easily? Electrons within a material allow current to flow These electrons have become ‘free’ from the atoms in the materials - some materials ‘give-up’ their electrons more easily

3. Good Conductor or Insulator? If it has a low Resistance, it lets more current through it - these are Conductors If it has a high resistance, it lets less current through it - these are called Insulators

4. How do we measure these characteristics? Resistance is measured in Ohms (Ω) Current is measured in Amperes (A) Voltage is measured in Voltage (V) Ohm’s Law V = I R

5. CONDUCTIVITY  - Sm -1 RESISTIVITY  m

6. Resistivity or Conductivity? Resistivity is the reciprocal of Conductivity Both are dependent on the material BUT: What are Resistance and Conductance?

7. Resistance Resistance is based on an individual object or component The resistivity of silver is 10 -8 Ωm but what is the resistance of a piece of silver wire?

8. Measuring the resistance of various wires Measure the resistance of various lengths of wire What happens when: you double the length? You double the cross-sectional area?

9. Resistance It depends on: The Cross-Sectional Area The Length and the resistivity (  ) of the material Resistance =  L / A in Ohms

10. Conductance The reciprocal of Resistance Resistance = 1 / Conductance Therefore Conductance (G) = L /  A or σ A / L (where σ is conductivity in Siemens m -1 )

11. Investigation Can we use these equations to calculate resistivity and conductivity? We need to measure length, cross-sectional area and resistance. We should be able to calculate the resistivity and/or conductivity of the material from the results