1. Write Down
• The three factors that resistance depends on.
• The value you got for your gradient.
• The value you worked out for the resistivity
(Gradient x Area).
4. Units
• R is measured in Ω
• ρ is measured in Ωm
• G is measured in S (Siemens)
• σ is measured in Sm-1
5. Temperature and Resistance in Metals
As temperature increases
the resistance within
metals increases.
This is because as the
temperature increases, the
lattice begins to vibrate
scattering the free
electrons in the metal.
This increases resistance.
6. Temperature and Resistance in Semi-
Conductors
As temperature increases
the resistance within semi-
conductors decreases.
This is because as the
temperature increases,
more electrons are freed to
move around.
This decreases resistance.
7. Work out the Error
• I measure the radius of a wire to be
0.0002±0.00005m
• I measure the length to be 0.10±0.005m
• What is the percentage error in my cross-
sectional area?
• What is the percentage error in my value of
resistance, assuming there are no other
errors?
