Resistance: Conduction in Different Materials

Conduction in Metal Charge carriers: Electrons For a metallic conductor, resistance increases as temperature increases Other factors affecting resistance of metallic conductors:Resistivity, length, cross-sectional area

Conduction in Ionic Solutions Charge carriers: Ions The conductivity of the solution increases with concentration Voltameter: combination of electrolyte, positive electrode (anode), negative electrode (cathode) and the container they are in Active electrodes: take part in the chemical reaction Inactive electrodes: do not take part in the reaction

This is a current-voltage graph for conduction in a metallic conductor Current increases with increasing voltage

This is a current-voltage graph for conduction in an ionic solution with active electrodes In an ionic solution with inactive electrodes the graph is a straight line that cuts the x-axis at a positive voltage. This is because a back emf must be overcome before current will flow

Conduction in Gases Charge carriers: Electrons A current-voltage graph for conduction in a gas discharge tube shows an initial increase in current with increasing voltage. It then plateaus before increasing again Neon lamps and street lights are examples of gas discharge tubes

Conduction in a Vacuum Charge carriers: Electrons The vacuum is maintained in a tube with electrodes at either end = a cathode ray tube A graph of current vs voltage for a cathode ray tube shows an initial increase in current with increasing voltage before it plateaus

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