The energy difference between the ground state and the first excited state

The energy difference between the superconducting state and the normal state

The energy difference between the Fermi level and the bottom of the conduction band

The energy difference between the top of the valence band and the bottom of the conduction band

The number of states per unit energy

The number of electrons per unit energy

The number of phonons per unit energy

The number of Cooper pairs per unit energy

It creates a gap in the density of states at the Fermi level

It shifts the density of states to higher energies

It shifts the density of states to lower energies

It does not affect the density of states

The energy gap is proportional to the critical temperature

The energy gap is inversely proportional to the critical temperature

The energy gap is independent of the critical temperature

The energy gap is equal to the critical temperature

Impurities decrease the energy gap

Impurities increase the energy gap

Impurities do not affect the energy gap

Impurities create a gap in the density of states at the Fermi level

Magnetic fields decrease the energy gap

Magnetic fields increase the energy gap

Magnetic fields do not affect the energy gap

Magnetic fields create a gap in the density of states at the Fermi level

The expulsion of magnetic fields from a superconductor

The attraction of magnetic fields to a superconductor

The increase in the energy gap in a superconductor in the presence of a magnetic field

The decrease in the energy gap in a superconductor in the presence of a magnetic field

The distance at which the magnetic field inside a superconductor is reduced to 1/e of its value at the surface

The distance at which the magnetic field inside a superconductor is reduced to 1/2 of its value at the surface

The distance at which the magnetic field inside a superconductor is reduced to 1/4 of its value at the surface

The distance at which the magnetic field inside a superconductor is reduced to 1/8 of its value at the surface

The distance over which the superconducting order parameter is correlated

The distance over which the superconducting energy gap is correlated

The distance over which the superconducting density of states is correlated

The distance over which the superconducting critical temperature is correlated

A theory that explains the existence of superconductivity in terms of the interaction between electrons and phonons

A theory that explains the existence of superconductivity in terms of the interaction between electrons and magnons

A theory that explains the existence of superconductivity in terms of the interaction between electrons and Cooper pairs

A theory that explains the existence of superconductivity in terms of the interaction between electrons and bosons

A pair of electrons that are bound together by the exchange of phonons

A pair of electrons that are bound together by the exchange of magnons

A pair of electrons that are bound together by the exchange of Cooper pairs

A pair of electrons that are bound together by the exchange of bosons

The temperature at which a superconductor loses its superconducting properties

The temperature at which a superconductor gains its superconducting properties

The temperature at which a superconductor has a zero energy gap

The temperature at which a superconductor has a zero density of states

The dependence of the critical temperature of a superconductor on the mass of its constituent isotopes

The dependence of the energy gap of a superconductor on the mass of its constituent isotopes

The dependence of the density of states of a superconductor on the mass of its constituent isotopes

The dependence of the coherence length of a superconductor on the mass of its constituent isotopes

A theory that describes the behavior of superconductors in the vicinity of their critical temperature

A theory that describes the behavior of superconductors in the vicinity of their zero temperature

A theory that describes the behavior of superconductors in the vicinity of their infinite temperature

A theory that describes the behavior of superconductors in the vicinity of their negative temperature

A lattice of magnetic flux lines in a superconductor

A lattice of electric flux lines in a superconductor

A lattice of Cooper pairs in a superconductor

A lattice of phonons in a superconductor