Resistivity And Superconductivity Flashcards
What 3 things determine the resistance of a length of wire
1) length- longer harder current flow
2) area- wider easier electrons pass through
3) resistivity- depends material
What is like resistance but doesn’t depend on size
Resistivity
Resistivity depends on the ….. The …. May make it easy or difficult for the charge to flow. In general, resistivity depends on the environmental factors as well, like …. And …. ….
Material
Structure
Temperature
Light intensity
What is the resistivity of a material defined as
The resistance of a 1m length with a 1m^2 cross-sectional area
What is resistivity measured in
Ohm-metres (the two symbols put together)
What is the equation for resistivity
R=pI/A
In what things are the typical values of resistivity really small
Conductors (e.g. Copper)
What resistivity do superconductors have
0
What does resistance caused conductors like silver and copper to do
When ELECTRICITY/CURRENT flows through them
They HEAT UP and some of the ELECTRICAL ENERGY is WASTED as HEAT
How can you lower the resistivity of materials like metals
By cooling them down
How do you make some materials into a superconductor
COOL them down below a ‘TRANSITION TEMPERATURE’
And there RESISTIVITY DISAPPEARS ENTIRELY
What can you do with no resistance
No ELECTRICAL ENERGY would be turned into a HEAT
So none is WASTED
Can start a CURRENT flowing in a CIRCUIT using a MAGNETIC FIELD,
TAKE away the magnet and the CURRENT would carry on flowing FOREVER
Why don’t we just make all ‘normal’ conductors e.g. Metals a superconductor
They have TRANSITION TEMPERATURES below 10 kelvin (-263C)
Getting things that COLD is HARD and really EXPENSIVE
What are solid-state physicists all over the world trying to develop
Room-temperature superconductors
What have solid-state physicists managed to get to conduct at (-133C)
Some weird metal oxide things
