b) Influences on resistance

ai) resistivity of a material; the equation R = L / A

in a wire, the resistance is influenced by

• the material of the wire

  • insulators, semiconductors, and conductors → different resistivities

• the temperature of the wire

  • high temperature → positive ions and electrons have more kinetic energy → larger vibrations → more collisions → higher resistance

• the length of the wire

  • longer wire → more positive ions → more collisions → higher resistance

• the cross-sectional area of the wire

  • larger cross-sectional area → more pathways for electrons to travel through → lower resistance