C3 - Resistivity and Conductivity Flashcards
Where do superconductors score on the logarithmic diagram?
> 10^8 conductivity or 10^-8 resistance.
Where do metals and metal alloys score on the logarithmic diagram?
They are slightly below super conductors. Alloys conduct less well compared to pure metals.
Where do semi-conductors score on the logarithmic diagram?
10^0 for conductivity and resistance.
Where do insulators score on logarithmic diagram?
10^-8 conductivity or 10^8 resistance.
How should conductance be measured in INSULATORS to reduce % uncertainty?
Use a large surface area to increase conductance, and use a sensitive ammeter, to obtain measurements easily.
How should resistance be measured in METALS to reduce % uncertainty?
A large length should be used to measure the resistance. Issues could arise from the PD dropping across the wire, alongside P=1^2R wire heating.
What are extensive properties?
These rely on dimensions such as length and area.
What are intensive properties?
These rely on material over specimen. A bulk constant is needed for resistance and conductance formulae.
When length is doubled, resistance…
What formula can represent resistance’s relationship to length?
Doubles.
R = pL/A
When cross-sectional area is doubled, conductance…
What formula can represent conductance’s relationship to area?
Doubles.
G = ōA/L
Resistivity is inversely proportional to…
Conductivity. p=1/o
How can a circuit be set up to measure conductivity?
Set up a cell with the component in series, and an ammeter to measure current. Attach a voltmeter in parallel. Measure the length using a rule, and diameter with a micrometer.
