Transcript Basic Principles of Electricity

Basic Principles of Electricity
Jennifer L. Doherty-Restrepo, MS, LAT, ATC
FIU Entry-Level ATEP
PET 4995: Therapeutic Modalities
Electromagnetic Spectrum
Longest
Wavelength
Shortest
Wavelength
Electrical Stimulating Currents
Commercial Radio and Television
Shortwave Diathermy
Microwave Diathermy
Infrared
LASER {
Visible Light
Ultraviolet
Ionizing Radiation
Lowest
Frequency
Highest
Frequency
Electrons
 Particles of matter possessing a ________
charge and a small ________
 Net movement of electrons is an ________
________
 Electrons will move from ________ to
________ energy levels
• Establishes an electrical ________
Electrical Potential Difference
 Difference in ________ of electrons
between two points
 Electrons will not move unless a ________
difference exists
Ampere
 Unit of measure which indicates _____ at
which electrons flow
• 1 _____ = movement of 1 coulomb or 6.25x1018
electrons /sec
 Current flow is typically described as:
• ________ (1/1000 of an amp), or
• ________ (1/1,000,000 or an amp)
Volt
 Creates the electrical potential ________
 The __________ ________ which must
be applied to create flow of electrons
 Commercial current (wall outlets) is either
________ or ________
Conductors
 Materials that permit ______ movement of
electrons
 Composed of large numbers of ________
electrons
 Offer ________ resistance to current flow
 Good conductors:
• Metals (copper, gold, silver, aluminum)
• Electrolyte solutions
Insulators
 Materials that ______ the flow of electrons
 Contain ________ free electrons
 Insulator materials:
• Air,
• Wood, and
• Glass
Resistance = Electrical Impedance
 ________ to flow of electrical current
 Measured in ________
• Unit of measure indicating resistance to
current flow
 Ohm’s law: current flow is ________
proportional to ________ and ________
proportional to ________
• Current flow =
Voltage
Resistance
Watt
 Measure of electrical ________
 Electrical ______ is the product of ______
(electromotive force) and the amount of
current flowing
• Watts = volts X amps
 Indicates the ________ at which electrical
power is being used
Electrotherapeutic Currents
 3 types of currents capable of producing
specific physiological effects
• ________
• ________
• ________
 Therapeutic effects of will be discussed in
Chapter 8
Direct Current (DC)
Uniterrupted, uniderectional flow of electrons in
the ________ direction
 Also called ________ currents
 Sometimes called ________ currents

Alternating Current (AC)

Continuous flow of electrons changes direction
• Always flows from ________ to ________ pole until
polarity is reversed

Also called ________ currents
Pulsitile (Polyphasic) Currents
________ electrical current that contains __ or
more grouped phases in a single pulse
 Also called ________ and ________ currents

Electrical Generators

Transcutaneous Electrical Nerve Stimulators
(TENS)
• Stimulates ________ ________

Neuromuscular Electrical Stimulator (NMES) =
Electrical Muscle Stimulator (EMS)
• Stimulates ________

Microcurrent Electrical Nerve Stimulators (MENS) =
Low Intensity Stimulators (LIS)
• Assists the ________ ________

All Are Transcutaneous Electrical Stimulators!
Electrotherapeutic Currents
 No relationship between type of current
used to power the generator and the type of
current transmitted to patient
 Generators may be powered by AC or DC
• Batteries = DC between 1.5 - 9 V
• Wall outlet = AC at 120 or 220V at 60 Hz
Waveform or Pulse
Pulse = ________
________
 Phases (duration)
 Interpulse interval
 Direction (polarity)
 Amplitude
 Rate of ________
 Rate of ________

• Accommodation
Symmetrical Waveforms
Sine
 Square
 Triangular
 Spiked


____ and _____
of each phase is
identical
Symmetrical Waveforms

Twin peaked
triangular waveform
• Found on most high
volt generators
Asymmetric Waveforms

________
• No longer used
• Effects were similar
to DC pulsed wave

________
• Sawtooth
• Used to stimulate
denervated muscle
Current Modulation
(A) Continuous
 (B) Interrupted
 (C) Burst

• Packets (envelopes)
• Pulse trains
• Beats

(D) Ramped (Surge)
Pulse Amplitude
Amplitude = current intensity = voltage
 ______ ______ = amount of current flowing per
unit time

• Determined by interpulse interval or current duration

Measured in ________ or ________
Pulse Duration
 Length of ________ current is flowing
 Monophasic current:
• ______ ______ = ______ ______
 Biphasic current:
• Pulse duration is determined by the combined
______ durations
 Polyphasic current:
• The combined pulse duration and interpulse
interval is the ______ ______
Pulse Frequency
 Number of ______ or ______ per second
• Measured as pulses per second (PPS)
 Individual pulse = rise and fall in amplitude
 As frequency ___________, amplitude
________ and ________ more rapidly
Pulse Frequency

Effects the type of muscle contraction
• Pulse rate of less than ___ pps = muscle twitch
• Pulse rate equal to or greater than ___ pps = tetany

Effects the mechanism of pain modulation
Electrical Circuits

Path of current from power source through
various components back to generating source
• ______ ______ : electrons are flowing
• ______ ______ : current flow ceases

Components of electrical circuits
• ______ ______: capable of producing voltage
• _________ _________: along which current travels
• _________ _________: providing resistance to
electrical flow
Series Circuit
Only ______ path for current to take
 Component resistors placed ______ to ______
 Total resistance = sum of resistances
 Total voltage = sum of voltage decreases

Parallel Circuit
Component resistors placed ___ to ___ and the
___ are connected
 Current chooses path with least _________

Series Circuit vs. Parallel Circuit
 Component resistors in a series circuit
have a ____ resistance and _____ current
flow
 Component resistors in a parallel circuit
have a _____ resistance and a _____
current flow
Current Flow Through Biologic
Tissues
Combination of both series and parallel circuits
 Tissue highest in water and ion content are the
best conductors

• Bood, nerve, muscle, tendon, skin, fat, bone
Physiologic Responses to Electrical
Current

Thermal
• All electrical currents cause a ____ in tissue
temperature
• Electrical currents used to stimulate nerve and muscle
produce _______ thermal effects

Chemical
• At ______ pole, negatively charged particles cause an
______ reaction
– Protein coagulation and hardening of tissues
• At ______ pole, positively charged particles cause an
______ reaction
– Liquefying protein and softening of tissues
Safety In Using Electrical
Equipment
Ground Fault Interrupters (GFI)
Constantly compare
amount of electricity
flowing from wall
outlet to whirlpool
turbine with the
amount returning
 GFI will interrupt
current flow in as
little as 1/40 of a
second

Summary
 Terminology
 Ohm’s Law
• Relationship between voltage and resistance
 Different types of current are capable of
producing specific physiologic changes
• Thermal or chemical
 Current modulation