Superconductivity
Physics: AQA A Level, topic 5.1.5
Superconductivity
Superconductors are materials with a resistivity of zero below a critical temperature.
Superconductors
- Because the resistance of a piece of a superconductor is zero, there are no heat losses for currents through them.
- This means that the current could flow forever.
- But most superconductors must be cooled to temperatures only a few Kelvin above absolute zero.
- This is very expensive and limits the use of superconductors.
Uses of superconductors
- Superconductors are used in magnets needing high currents, such as in MRI machines.
- If we could make our power lines superconductors they would cut energy losses in power transmission.
- Recently advancements have been made which mark progress towards making superconductors work at room temperature.
Applications of Superconductors
Superconductors have zero resistance. This is a useful quality and is used in many applications.
Zero resistance
- Superconductors occur when free electrons combine to form Cooper pairs at low temperatures.
- These Cooper pairs collide with the other atoms in the material and, if the energy of the collision is low, then the Cooper pairs do not split and lose energy.
- This means that the resistivity of the superconducting material is zero.
Magnetic fields
- Moving charges produce magnetic fields.
- If the charges move less, the magnetic field strength reduces.
- There needs to be a constant movement of charge to maintain a large magnetic field.
- With high resistance situations, this requirement would result in a lot of excess heat.
- Magnets made of superconductors have zero resistivity so that once currents have been set up, they continue without loss of energy.
Reduction of energy loss
- Superconductors can also reduce energy loss in energy transmission.
- Cables made of superconductors would have no power losses.
Test yourself on Superconductivity
At what temperatures do superconductors work?
Which of these statements are true of superconductors?
Which statements about superconductors are true?
How do free electrons in a superconductor travel?