Resistivity And Superconductors Flashcards
What is the unit of resistivity?
Ohm-metres.
Define “resistivity”.
The resistance of 1m length with a 1m^2 cross-sectional area.
What are the three elements that resistance depends on?
- length
- area
- resistivity
Why does length effect resistance?
The longer the wire, the more difficult it is to make a current flow through it, thus increasing resistance.
What is the relationship between resistance and length of the wire?
The resistance is proportional to the length of the wire.
Why does area effect resistance?
The wider the wire, the easier it is for the electrons to pass along it, thus reducing resistance.
What is the equation for calculating resistivity?
Resistivity = (resistance x cross-sectional area)/length
How can resistivity be lowered in most materials?
Cool them down.
How can a material become a superconductor?
A material cooled down to below a “transition temperature”.
What is the transition temperature for most “normal” (metal) conductors? Why is this a problem?
10 kelvin (-263 degrees). It is difficult and expensive to get a material to reach this temperature.
State three uses of superconductors.
- power cables that transmit electricity without any loss of power.
- strong electromagnets.
- fast electronic circuits.
