Intro to EPA Flashcards
Conduction current flows in ________.
conductors
Convection current flows in ______ or ____.
fluids; gases
Current is measured in ?
amperes
Conduction current = _________ material in which the outer shell electrons are free to move between the fixed atoms.
crystalline
Convection current flows via the movement of ____.
ions
Positive ions = ?
cations
Negative ions = ?
anions
You need an ______ between conduction current and convection current.
interface
Current flows in electrolyte solutions or plasma in which direction(s)?
Both from positive to negative and vice versa
_______ = the electric charge carried by a current of one ampere, flowing for one second
coulomb
______ = the basic unit of measured charge
coulomb
______ = the rate of flow of current; current intensity
ampere
1 ampere = ?
1 C/s
______ = the measure of energy difference between two physical points
volt
1V = ?
1J/C
What is resistance measured in?
Ohms
Does dry or wet epidermis have higher resistance?
Dry
What is Ohm’s law?
V = IxR
_____ = the rate of converting energy
watt
1W = ?
1 J/sec
What two things does current density depend on?
- amount of current
2. cross section of the wire / area of electrode
What are 3 ways to minimize current density in treatment?
- adequate electrode size
- electrodes are in good condition
- lowest intensity for therapeutic benefit
A _______ = two conductors separated by an insulator
capacitor
_______ = stores electric charge, and current frequency determines resistance to current flow
capacitor
Dry epidermis impedes the passage of electric current, and it is a combination of what 3 things?
- Ohmic resistance
- Capacitive reactance
- Inductive reactance (minimally important)
_____ _______ = a materials opposition to the flow of electric current, measured in ohms
ohmic resistance
_____ _______ = the opposition to current flow provided for a capacitor, is measured in ohms and varies inversely with frequency
capacitive reactance
What 3 things does skin resistance depend on?
- Dry or wet skin
- Pulse duration
- Current intensity
What current has the highest impedance?
Direct current
Do you want electrical devices with constant voltage or constant current?
constant VOLTAGE!
________ = formation of new chemical compounds
electrochemical
________ = stimulation of excitable tissue
electrophysical
________ = production of heat
electrothermal
Electrochemical occurs with _________ current only
unidirectional
Electrochemical charges can cause blistering or chemical burns (T/F)?
TRUE
Electrophysical effects are caused by _______ movement.
ionic
Ionic movement in ________ effects causes indirect responses such as muscle contraction, activate endogenous analgesic mechanisms, vascular responses
electrophysical
_________ = heating caused by friction from movement of charged particles in a conductive medium
electrothermal
_______ _____ = electrical stimulation results in the movement of ions
cellular signalling
What are 4 cellular effects observed in response to applied electric current?
- enhanced ATP synthesis
- DNA synthesis
- Facilitating activity of other enzymes
- Cytokine release
What are 3 types of current?
- direct
- alternating
- pulsed
What are 3 fundamental questions before treatment?
- what effect is intended and can this treatment achieve this effect?
- is it safe?
- is this the best method of treatment to achieve this effect?
What are 4 clinical applications or therapeutic modalities?
- Modulation of pain
- Alteration of skeletal muscle performance (facilitation and inhibition)
- Decrease inflammation and facilitating tissue healing
- Increase tissue extensibility
Tissue damage from passage of electric currents can occur in what 3 ways?
- direct of phasic currents can cause chemical burns
- currents that stimulate nerve of muscle (powerful or prolonged contraction of muscles)
- high current density can cause burns through tissue heating
Chemical burns can occur using direct and alternating current (T/F).
FALSE ; just DC; AC would not allow the build up of new compounds under each electrode
_____shock = current passes into body through skin
macro
___mA of current may be fatal in macroshock
100
___shock = current passes directly to heart
micro
__uA may cause ventricular fibrillation
20 (micro?)
In macroshock, what is important is the total electric charge - this includes both the _____ and ____ of the current (as well as path it travels through body)
amplitude; duration
In macroshock, ____ is the primary variable that determines the severity of the shock.
current
All non-battery therapeutic devices must use a ___pin plug.
3
