Basic Principles of Basic Principles of ElectricityElectricity

Jennifer L. Doherty-Restrepo, MS, LAT, ATCFIU Entry-Level ATEPPET 4995: Therapeutic Modalities

Electromagnetic SpectrumElectromagnetic Spectrum

Electrical Stimulating CurrentsElectrical Stimulating CurrentsCommercial Radio and TelevisionCommercial Radio and Television

Shortwave DiathermyShortwave DiathermyMicrowave DiathermyMicrowave Diathermy

InfrareInfrareddLASERLASER

Visible LightVisible Light

UltravioletUltraviolet

Ionizing RadiationIonizing Radiation

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LongestLongestWavelengthWavelength

ShortestShortestWavelengthWavelength

LowestLowestFrequencyFrequency

HighestHighestFrequencyFrequency

ElectronsElectrons

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 Electrical Potential DifferenceDifference

Difference in ________ of electrons between two points

Electrons will not move unless a ________ difference exists

AmpereAmpere

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)

VoltVolt

Creates the electrical potential ________

The __________ ________ which must be applied to create flow of electrons

Commercial current (wall outlets) is either ________ or ________

ConductorsConductors

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

InsulatorsInsulators

Materials that ______ the flow of electrons

Contain ________ free electrons Insulator materials:

• Air, • Wood, and • Glass

Resistance = Electrical Resistance = Electrical ImpedanceImpedance

________ 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

WattWatt

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 Electrotherapeutic CurrentsCurrents

3 types of currents capable of producing specific physiological effects• ________• ________ • ________

Therapeutic effects of will be discussed in Chapter 8

Direct Current (DC)Direct Current (DC)

Uniterrupted, uniderectional flow of electrons in the ________ direction

Also called ________ currents Sometimes called ________ currents

Alternating Current (AC)Alternating Current (AC)

Continuous flow of electrons changes direction• Always flows from ________ to ________ pole until

polarity is reversed Also called ________ currents

Pulsitile (Polyphasic) Pulsitile (Polyphasic) CurrentsCurrents

________ electrical current that contains __ or more grouped phases in a single pulse

Also called ________ and ________ currents

Electrical GeneratorsElectrical 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!All Are Transcutaneous Electrical Stimulators!

Electrotherapeutic Electrotherapeutic CurrentsCurrents

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 PulseWaveform or Pulse

Pulse = ________ ________

Phases (duration) Interpulse interval Direction (polarity) Amplitude Rate of ________ Rate of ________

• Accommodation

Symmetrical WaveformsSymmetrical Waveforms

Sine Square Triangular Spiked

____ and _____ of each phase is identical

Symmetrical WaveformsSymmetrical Waveforms

Twin peaked triangular waveform• Found on most high

volt generators

Asymmetric WaveformsAsymmetric Waveforms

________ • No longer used No longer used • Effects were Effects were

similar to DC similar to DC pulsed wavepulsed wave

________ • SawtoothSawtooth• Used to stimulate Used to stimulate

denervated muscledenervated muscle

Current ModulationCurrent Modulation

(A) Continuous (B) Interrupted (C) Burst

• Packets (envelopes)

• Pulse trains• Beats

(D) Ramped (Surge)

Pulse AmplitudePulse Amplitude

Amplitude = current intensity = voltage ______ ______ = amount of current flowing

per unit time• Determined by interpulse interval or current

duration Measured in ________ or ________

Pulse DurationPulse 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 Pulse Frequency

Number of Number of ______ or or ______ per per secondsecond• Measured as pulses per second (PPS)Measured as pulses per second (PPS)

Individual pulse = rise and fall in Individual pulse = rise and fall in amplitudeamplitude

As frequency As frequency ___________, , amplitude amplitude ________ and and ________ more rapidlymore rapidly

Pulse Frequency 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 CircuitsElectrical 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 CircuitSeries Circuit

Only ______ path for current to take Component resistors placed ______ to ______ Total resistance = sum of resistances Total voltage = sum of voltage decreases

Parallel CircuitParallel Circuit

Component resistors placed ___ to ___ and the ___ are connected

Current chooses path with least _________

Series Circuit vs. Parallel Series Circuit vs. Parallel CircuitCircuit

Component resistors in a series Component resistors in a series circuit have a circuit have a ____ resistance and resistance and _____ current flow current flow

Component resistors in a parallel Component resistors in a parallel circuit have a circuit have a _____ resistance and resistance and a a _____ current flow current flow

Current Flow Through Current Flow Through Biologic TissuesBiologic 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 Physiologic Responses to Electrical CurrentElectrical Current

ThermalThermal• All electrical currents cause a All electrical currents cause a ____ in tissue in tissue

temperature temperature • Electrical currents used to stimulate nerve Electrical currents used to stimulate nerve

and muscle produce and muscle produce _______ thermal effects thermal effects ChemicalChemical

• At At ______ pole, negatively charged particles pole, negatively charged particles cause an cause an ______ reaction reaction – Protein coagulation and hardening of tissuesProtein coagulation and hardening of tissues

• At At ______ pole, positively charged particles pole, positively charged particles cause an cause an ______ reaction reaction– Liquefying protein and softening of tissuesLiquefying protein and softening of tissues

Safety In Using Electrical Safety In Using Electrical EquipmentEquipment

Ground Fault Interrupters Ground Fault Interrupters (GFI)(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

SummarySummary

TerminologyTerminology Ohm’s Law Ohm’s Law

• Relationship between voltage and Relationship between voltage and resistanceresistance

Different types of current are capable Different types of current are capable of producing specific physiologic of producing specific physiologic changeschanges• Thermal or chemicalThermal or chemical

Current modulationCurrent modulation