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All materials conduct somewhat, all materials resist conduction somewhat,
Those materials that conduct lots and resist little are called Conductors
Those materials that conduct little and resist lots are called Insulators
In order to understand this section we need to know the basics about charges
So after that we know that protons have a positive charge and are very massive compared to the electrons mass, and as the electron is negative then it is the opposite charge
Conduction
Electrical conduction is the transfer of charge from one place to another place. This can occur in many diffrerent types of materials. These different materials differ in properties due to the types of bonding that holds them together.
Conduction is usually down to the transfer of electrons from one side of the conductor to the other, however in some cases it can be apparent positive charges that move.
in
• metals
Metals are held together by metallic bonding. In essence the atoms sit in lattices with their outer orbits overlapping. This effectively means that the electrons in the outermost orbits are, on average, outside the atom ?!?!? and the positive nucleas has not much hold on them as there are so many electrons in this region. Therefore while the overall charge on a metal is neutral
the best conductors are silver, copper, gold, aluminum, calcium, beryllium, tungsten
The curve of conduction in metallic conductors ... can be drawn from carrying out the experiment below.
Amazing page on this site with some very excellent ideas on bonding ....
especially the metallic bonding idea
http://www.uwgb.edu/dutchs/EarthSC202Notes/minerals.htm
• ionic solutions (active and inactive electrodes)
• gases
Gases do conduct electricity, as all materials do. However, they conduct electricity so poorly that we consider them insulators. "Electricity" requires the movement of electrons. In a gas, these electrons are too dispersed to provided any measurable current.
Electric discharge in gases. Electric discharge in gases occurs when electriccurrent flows through a gaseous medium due to ionization of the gas. Depending on several factors, the discharge may radiate visible light.
Neon lamps, street lights.
Car Headlight Bulb, H7 12V, 55W Halogen
• vacuum
• semiconductors.
A semiconductor is a material that has a resistivity between that of a conductor (very low) and an Insulator (very high).
Semiconductors are usually based on the Group IV elements Silicon and Germainium. These elements naturally form crystalline solids. The conductivity of these substances changes dramatically with changes in temperature.
Semiconductors can also be doped (intrinsic conduction) to help control their conductivity profile.
for more on semiconductors go here
References in each case to charge carriers.
Mandatory experiments
5. To investigate the variation of current (I ) with pd (V ) for
(a) metallic conductor
(b) filament bulb
(c) copper sulfate solution with copper electrodes
(d) semiconductor diode.
Electronic devices.
LED, computers, integrated circuits.
Rectification of a.c.
Interpretation of I–V graphs.
Demonstration of current flow across a p-n junction in forward and reverse bias, e.g. using a bulb.
Forward Bias, needs a protective resistor, can be removed when attempting to reverse bias .... and change the milli ammeter with a micro ammeter
back to current
on to resistance
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