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Key equations

Electrostatic energy for equilibrium separation distance between atoms U coul = k e 2 r 0
Energy change associated with ionic bonding U form = E transfer + U coul + U ex
Critical magnetic field of a superconductor B c ( T ) = B c ( 0 ) [ 1 ( T T c ) 2 ]
Rotational energy of a diatomic molecule E r = l ( l + 1 ) 2 2 I
Characteristic rotational energy of a molecule E 0 r = 2 2 I
Potential energy associated with the exclusion principle U ex = A r n
Dissociation energy of a solid U diss = α k e 2 r 0 ( 1 1 n )
Moment of inertia of a diatomic molecule with reduced mass μ I = μ r 0 2
Electron energy in a metal E = π 2 2 2 m L 2 ( n 1 2 + n 2 2 + n 3 2 )
Electron density of states of a metal g ( E ) = π V 2 ( 8 m e h 2 ) 3 / 2 E 1 / 2
Fermi energy E F = h 2 8 m e ( 3 N π V ) 2 / 3
Fermi temperature T F = E F k B
Hall effect V H = u B w
Current versus bias voltage across p-n junction I net = I 0 ( e e V b / k B T 1 )
Current gain I c = β I B
Selection rule for rotational energy transitions Δ l = ± 1
Selection rule for vibrational energy transitions Δ n = ± 1

Conceptual questions

Describe two main features of a superconductor.

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How does BCS theory explain superconductivity?

BSC theory explains superconductivity in terms of the interactions between electron pairs (Cooper pairs). One electron in a pair interacts with the lattice, which interacts with the second electron. The combine electron-lattice-electron interaction binds the electron pair together in a way that overcomes their mutual repulsion.

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What is the Meissner effect?

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What impact does an increasing magnetic field have on the critical temperature of a semiconductor?

As the magnitude of the magnetic field is increased, the critical temperature decreases.

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At what temperature, in terms of T C , is the critical field of a superconductor one-half its value at T = 0 K ?

T = 0.707 T c

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What is the critical magnetic field for lead at T = 2.8 K ?

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A Pb wire wound in a tight solenoid of diameter of 4.0 mm is cooled to a temperature of 5.0 K. The wire is connected in series with a 50 - Ω resistor and a variable source of emf. As the emf is increased, what value does it have when the superconductivity of the wire is destroyed?

61 kV

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A tightly wound solenoid at 4.0 K is 50 cm long and is constructed from Nb wire of radius 1.5 mm. What maximum current can the solenoid carry if the wire is to remain superconducting?

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Additional problems

Potassium fluoride (KF) is a molecule formed by an ionic bond. At equilibrium separation the atoms are r 0 = 0.255 nm apart. Determine the electrostatic potential energy of the atoms. The electron affinity of F is 3.40 eV and the ionization energy of K is 4.34 eV. Determine dissociation energy. (Neglect the energy of repulsion.)

U coul = −5.65 eV E form = −4.71 eV , E diss = 4.71 eV

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For the preceding problem, sketch the potential energy versus separation graph for the bonding of K + and Fl ions. (a) Label the graph with the energy required to transfer an electron from K to Fl. (b) Label the graph with the dissociation energy.

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The separation between hydrogen atoms in a H 2 molecule is about 0.075 nm. Determine the characteristic energy of rotation in eV.

E 0 r = 7.43 × 10 −3 eV

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The characteristic energy of the Cl 2 molecule is 2.95 × 10 −5 eV . Determine the separation distance between the nitrogen atoms.

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Questions & Answers

plot a graph of MP against tan ( Angle/2) and determine the slope of the graph and find the error in it.
Ime Reply
expression for photon as wave
Are beta particle and eletron are same?
Amalesh Reply
how can you confirm?
If they are same then why they named differently?
because beta particles give the information that the electron is ejected from the nucleus with very high energy
what is meant by Z in nuclear physic
Shubhu Reply
atomic n.o
no of atoms present in nucleus
Note on spherical mirrors
Shamanth Reply
what is Draic equation? with explanation
M.D Reply
trpathy Reply
it's a subject
it's a branch in science which deals with the properties,uses and composition of matter
what is a Higgs Boson please?
god particles is know as higgs boson, when two proton are reacted than a particles came out which is used to make a bond between than materials
bro little abit getting confuse if i am wrong than please clarify me
the law of refraction of direct current lines at the boundary between two conducting media of
what is the black body of an ideal radiator
Areej Reply
uncertainty principles is applicable to
what is the cause of the expanding universe?
microscopic particles or gases
Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pulling galaxies apart. One explanation for dark energy is that it is a property of space.
Thanks for your contribution Areej.
no problem
what is photoelectric equation
How does fringe intensity depend upon slit width in single slit diffraction?
Abhishek Reply
intensity seems to be directly proportional radius of slit
what are the applications of Bernoulli's equation
Md Reply
what is Draic equation
about nuclear angular momentum
rahul Reply
what is spin
Practice Key Terms 6

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