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15 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Name:


Teacher:


Your task

You may use the following questions as a basis for your answer.

Metal crystals

Describe the structure of a metallic lattice crystal.

State the technology that enabled scientists to work out the crystal lattice
structure.


T
he Braggs

The contribution of the Braggs to an understanding of the crystal structure is
undisputed. Assess the impact of their contribution to the understanding of the
crystalline structure of materials.

Science is a progression of knowledge. The Braggs
built on the work of other
scientists. Outline the important discoveries that were useful for their work.

Describe the method used by the Braggs

to work

out the structure of crystals
.

Explain why X
-
rays and not visible or
why
ultraviolet light was the best

wavelength to use in the discovery of crystal structure.


Conduction in metals

Identify two factors that affect the actual number of electrons

per second

that
can flow along a particular conductor.

Explain why drift velocity of electrons in metals is low
er than expected.





Resistance in metals

Identify four different types of lattice defects.

Describe the passage of an electron through the crystal lattice.


Superconductors

Describe superconductivity.

Identify and name two superconductors that operate

in liquid nitrogen and two
that require liquid helium.

Explain why the development of higher temperature superconductors is of
such importance.

Each superconductor has a critical temperature. Represent this using a graph
and explain what happens when the
critical temperature is reached.


BCS theory

Outline the BCS theory.

Describe the passage of a pair of electrons through the crystal lattice structure
during superconduction.

In the BCS theory
,

explain the role of Cooper pairs and phonons.


Superconduct
or types

Explain the difference between Type I and Type II superconductors
.

Name three Type I and three Type II superconductors. Give the critical
temperature for each of these.

Why is the search for higher temperature superconductors so important?

S
earch

the Internet for the
current
highest temperature superconductor
discovered.





Applications

List five possible applications for superconductors.

Describe

the advantages of using superconductor technology to make better
el
ectric motors or electromagnets
.

Superconductivity has the potential to be used in many applications. Choose
one application. Discuss the advantages and limitations of using
superconductors in that application.


Maglev train

Discuss the advantages of a maglev train
.

Describe the propul
sion of a maglev train.


Meissner effect

Describe the Meissner effect.

In the experiment
,

state

th
e importance of liquid nitrogen.

List
the safety precautio
ns required for this experiment.

Carry out a risk assessment on this experiment.


Advantages and l
imitations

List the advantages of superconductors
.

List some of the limitations of superconductors.


Summary

Discuss how this technology has changed your day
-
to
-
day life.