Magentism & Electricity Flashcards
Electrodynamics
The study of electrical charges in motion
Electrostatics
The study of stationary electric charges
Electrified
To produce electric charge on or in a conductor
Electric ground
Reference point in an electrical circuit from which voltages are measured.
A common return path for electric current.
A direct physical connection to the earth.
Electrostatic force
The attraction or repulsion of particles or objects because of their electric charge.
Potential/potential difference
AKA voltage
Voltage/electromotive force (EMF)
The force that propels electrons.
Current
The flow of electrons measured in amperes.
Direct current - DC - Edison
Alternating current - AC -Westinghouse
Amperage
AKA Current/Impedance
The number of electrons in motion
1 Amp = 6.3x10 to the 18th electrons per second
Conductor
Material that readily allows the flow of electrons.
Insulator
Material that does not allow the flow of electrons.
Semiconductor
Under some conditions it acts as a conductor and other others as an insulator.
Circuit
Path over which electrons flow.
Direct current (DC)
Current that contains a constant magnetic field, electron flow in only one constant direction. (Edison)
Alternating current (AC)
Current that contains a changing magnetic field, electron flow in a back and forth motion, changing directions, oscillating. (Westinghouse)
Wattage/Watt (W)
The unit of electrical power.
Volts x Amps = Watts
Electrical resistance
The force that opposes the flow of electrons.
Ohm
Measurement used for resistance
Resistor
Inhibits electron flow.
Magnetism/inverse square law
Intensity of the magnetic attraction or repulsion is inversely proportional to the square of the distance from the magnet.
Natural permanent magnet
Occur in nature found in/on earth, “always on”, i.e. Iron oxide.
Artificial permanent magnet
Man made, “always on”, i.e. Steel alloy of aluminum, nickel, cobalt, ALNICO
Electromagnet
Man made temporary magnets, a solenoid with an iron core
Electromagnet advantages
On/off switch.
Variable magnetic field.
Simple to produce.
Ferromagnetic
Highly magnetic material.
Highly attracted to iron.
I.E. Iron, nickel, cobalt, ALNICO.
Paramagnetic
Slightly magnetic material.
Slightly attracted to iron.
I.E. Platinum, aluminum, gadolinium
Diamagnetic
Always repelled by magnets (either north or south).
I.E. Lead, beryllium, bismuth
Nonmagnetic
Not influenced by magnets at all, neither attracted or repelled by magnets.
I.E. Wood, glass, rubber, paper, plastic.
Good insulator.
Induction
To influence without contact
Magnetic lines of force/lines of flux
AKA magnetic fields; flow inside and outside of a magnet form a 3 dimensional field around a magnet, undetectable to the human senses.
Tesla/gauss
Magnetic field strength measurements.
1 Gauss = approximate magnetic field of earth.
1 Tesla = 10,000 gauss
Series circuit.
All elements are connected in a line along the same conductor.
Total resistance is the sum of all resistors.
Current is the same over each resistor and equal to total circuit current.
Sum of voltage across each circuit element is equal to entire current voltage.
Parallel circuit
Contains elements that are connected on the ends and not lying along a conductor.
The sum of the currents thru each circuit elements is equal to the total circuit current.
The voltage across each circuit element is the same and equal across each circuit element.
Total resistance is the inverse of the the of the reciprocals of each individual resistor.
Electric motor
Machine that converts electrical energy into mechanical energy.
Electrical generator
Device that converts mechanical energy to electrical energy.
Coil
Wound loops of wire
Solenoid
A coil with current flow.
Transformer
Increase or decrease voltage, electrical component that reconfigures wattage.
Autotransformer
An electrical transformer with only one winding.
Rectifier/Diode
Electrons flowing in only one direction.
Capacitor
Stores electric charge temperature.
Ohms Law
The voltage across the outer circuit of any portion of the circuit is equal to the current x resistance (V=IxR)
Orested’s Law
Charged particles in motion will produce a magnetic field that is perpendicular to their plane in motion.
Faraday’s Law
A changing magnetic field will induce current flow in a conductor that is with in the magnets sphere of influence
Magnetic fields
Always have a north and South Pole.
Like poles and opposite poles work as electrical particles will.
Opposite poles attract/like poles repel.
Electromagnets - variable strength
The number of loops of wire in a solenoid allow variable strength. The more windings the greater magnetic field strength.
2 important functions electromagnets serve in the X-ray circuit.
1: Transformers (3)
- autotransformers
- step up transformer
- step down transformer
2: induction motor in the tube
Why an iron core?
Is induced to move by the electromagnet.
OR
Captures and intensifies the magnetic field produced by the solenoid.
Superconduction
Cooling the temperature of a coil of wire to the point that there is virtually no resistance to the flow of electrons.
As amperage goes up magnetic strength goes up.
Laws of magnetism
Repulsion and attraction
-like charges repel/opposites attract
Force of attraction
-as distance increases force of attraction decreases
Bipolar
Every magnet has two poles (north and south). If you break a magnet in 2 you have 2 smaller magnets.
Permeability
The ease with which a material can be magnetized.
Retentivity
The ability of a material to stay magnetized
Step up transformer
Voltage is increased from primary to secondary.
Step down transformer
Voltage is decreased from primary to secondary
Transformer stepping
How voltage is affected from primary to secondary.
Electrification
Occurs when an object has too many it too few electrons
Contact
When objects touch their charges “spread out” equally
Friction
When objects rub together electrons are transferred
Induction
Influenced without contact.
Coulomb’s law
The electrostatic force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
Electrical power
Unit: Watt
Power=volts x current
PIV
Transformers
Electrical component that reconfigures wattage.
Primary - side of transformer initially supplied with current
Secondary - side of transformer in which current is induced to flow
Series circuit resistance
Rt = R1 + R2 + R3…
Meaning
Resistance total equals resistance in circuit one plus circuit two plus circuit three.
Parallel circuit resistance
1/Rt = 1/R1 + 1/R2 + 1/R3…
Meaning
Resistance total is the reciprocals of the total of the various circuits.
