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Transcript
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