Lecture 10 Flashcards
Electric current
The directional movement of electric charge
Current is the amount of charge which flows through the conductor per unit of time
Unit is ampheres.
Current density
The current per cross sectional area of the conductor
Electromotive force
The electric field in the conductor is created by external agents and the electromotive force is the amount of the work the external agent has to carry out to move a positive charge across the conductor.
Conductance and resistance
The current I glowing through a conductor is directly proportional to the applied voltage U.
I=GU
Polar molecules
Is when the positive and negative charges are separated in space eg. Water.
Solvation
This is when the ions obtained by the dissociation of the dilute are surrounded by the polar solvent molecules.
Recombination
Is when the bonding of ions with opposite charges in the solution producing neutral molecules.
Dissociation constant
Depends on the relative permittivity of the solvent and the dipole moment of the solute molecules.
Conductivity of electrolytes
It depends on concentration and temperature.
Conductivity of biological tissues
They are made up of proteins, Lipids and ionic solution. But proteins and lipids have a low conductivity.
Bones and dry skin have low conductivity whereas blood has high conductivity.
The flow of electric current through the human body
The total electric resistance of the body is mainly determined by the resistance of the skin.
The electric current passes through the skin through the pores of the sweat glands.
Diagnostic indicator
To show inflammation and increased blood supply
Rheography is a way.
Conductivity of gases
A pure gas consists of neutral atoms or molecules and gases do not contain free charge carriers.
Impact ionization
This is when neutral atoms can be ionized on collision with fast moving particles
Volt amphere characteristic of a gas discharge
Gas discharge is when there is the flow of electric current in a gas.
The current consists of an electronic and two ionic streams.
Self sustain discharge
Avalanche discharge is when impact ionization takes place at these high voltages and the number of charge carriers produced in the gas per unit of Time increases rapidly.
Air ions
The air ions which are mainly Ionised N2 and O2.
The small negative air ions produce a tonic effect and all the other types of air ions are considered harmless
