Electrons (2) Flashcards
When a valence electron in any atoms gains sufficient energy, it can:
break away from the parent atom and become a free electron
After a valence electron becomes a free electron the vacancy:
must be replace by another to maintain the electrical balance within the atom
External force that acts upon a material will cause electrons to ___ in the ____ of the force
flow in the direction of the force. (electrical current)
Define Electrical Current (I)
the movement of electrons through a conductor
- amperes (amps)
- 1amp = electrical current that exists when a number of electrons having 1 coulomb of charge, moves past a given point in 1 second.
What is a Coulomb?
charge carried by 6.25x10¹⁸ electrons
Direct Current (DC)
continuous + flow
Alternating Current (AC)
- 60 cycles per second at 15-20 amps
- skin effect
- Nikola Tesla
Describe Electromotive Force EMF (Voltage)
1 volt = electrostatic difference between 2 points when 1 J of energy is used to move 1 C from point a to b.
A J = energy consumed when 1 w of power works for 1 sec (watt-second)
Define electrical resistance
the opposition to the flow of electrons within an electric circuit.
- limits amount of current flow
- low resistance - good conductor (copper)
- high resistance - good insulator (rubber)
- varies with cross section and length of conductor (short cross section = more resistance, short length = less resistance)
Resistance formula
R = p x I / A p = R x I / A
R - electrical resistance (ohms)
p = resistivity (ohm/m)
I = length (m)
A = cross section (m²)
Resistivity value for Annealed Copper
1.72x10⁻⁸ohm/m
Define conductivity
opposite of resistivity
ability to conduct electrical current (sigma o)
Conductivity formula
o = 1 / p
o = conductivity (S/m⁻¹) p = resistivity (ohm/m)
Ohms law
1826 Georg Simon Ohm
1 volt of electrical pressure (v) will force 1 amp of current flow (I) through 1 ohm (R) of electrical resistance.
V = I x R
Typical frequency ranges for current flow in ET coils
Hz per second
100Hz - 10MHz
