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Physics Section 3: Current Electricity > Resistivity And Superconductivity > Flashcards

Flashcards in Resistivity And Superconductivity Deck (16)
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0

What is like resistance but doesn't depend on size

Resistivity

1

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

2

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

3

What is the resistivity of a material defined as

The resistance of a 1m length with a 1m^2 cross-sectional area

4

What is resistivity measured in

Ohm-metres (the two symbols put together)

5

What is the equation for resistivity

R=pI/A

6

In what things are the typical values of resistivity really small

Conductors (e.g. Copper)

7

What resistivity do superconductors have

0

8

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

9

How can you lower the resistivity of materials like metals

By cooling them down

10

How do you make some materials into a superconductor

COOL them down below a 'TRANSITION TEMPERATURE'
And there RESISTIVITY DISAPPEARS ENTIRELY

11

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

12

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

13

What are solid-state physicists all over the world trying to develop

Room-temperature superconductors

14

What have solid-state physicists managed to get to conduct at (-133C)

Some weird metal oxide things

15

What uses can you get out of superconductors

1) power cables- that transmit ELECTRICITY without any LOSS of power
2) really strong ELECTROMAGNETS- that DONT need a CONSTANT POWER source (use in medical applications & maglev trains)
3) ELECTRONIC CIRCUITS- that work really FAST because there is no RESISTANCE to slow them DOWN