BPA Unit 4: Electrophysics Flashcards
(48 cards)
What is a Charge?
A fundamental property of electromagnetic force and underlies the mechanisms by which living cells communicate with one another, that being depolarizing and repolarizing.
- The charge is obtained by the addition or removal of electrons and occurs when atoms of elements are acted upon by external physical forces such as friction, heat, and chemical or electrical sources. (Unit = Coulombs)
What is Ionization?
The process by which an atom or molecule acquires a negative or positive charge
What are the 4 fundamental properties of electrical charge
- There are two types of charge—positive and negative.
- Like charges repel while opposites attract.
- Charge is neither created nor destroyed.
- Charge can be transferred from one object to another.
With a charge, what does polarity refer to?
This refers to the net charge of an object - being either negative or positive
What is the difference between Anode and Cathode?
Anode is positive
{Attracts anions = negative ions}
- It has more electrons than protons
Cathode is negative
{Attracts Cations = positive ions}
- It has more protons than electrons
What is Voltage?
The force of attraction or repulsion created by an electric field represents potential energy. The greater the force, the greater the potential energy
- This force is termed voltage and represents the driving force that moves electons
- Measures in volt (V) or milivolt (mV)
What are Conductors and Isolators?
- Conductors are materials in which the ions and electrons move freely
-Tissues as muscle, nerves, and body fluid serve as conductors - Insulators are materials in which charged particles are not free to move or do not move easily
-Plastic and/or rubber
What is a current?
The movement of ions or electrons in a conductor in response to a voltage force
- Current symbol = I
- Unit = Amperre (A) or milliamperes (mA)
With Ohm’s Law, what is Resistance?
Resistance is opposition to the flow of current and comes in many forms in the body
With Ohm’s Law, what is Capacitance and Impedance?
- Capacitance is the degree to which electrical charge is stored in a system containing conductors and insulators, such as the human body
- Impedance is the resistance to the flow of alternating current, whereas resistance is specific to direct current. Gels and adhesive conductive agents on electrodes serve to decrease impedance and increase conductivity between the electrode and skin
How are currents and waveforms represented on a graph?
The horizontal axis denotes duration while the vertical axis represents the magnitude or intensity (amplitude) of the current (Ampere, mA or volts)
What is a Direct Current (DC)?
This is the continuous unidirectional flow of ions or electrons for at least 1 second
- The term direction implies flow from positive to negative or negative to positive
What are the most common clincal uses for Direct Current?
- For Iontophoresis
- Wound Care
What is an Alternate Current (AC)?
This is the uninterrupted bidirectional flow of ions or electrons and must change direction at least one time per second
What is Pulsed Current (PC)?
This is the uni- or bidirectional flow of ions or electrons that periodically ceases for a period of time before the next electrical event
With Pulsed Current what is the effect on Muscle Stimulation?
Ssed for stimulating skeletal muscle for strengthening and activity.
- Because PC is a series of pulses, muscle
fibers can be stimulated frequently, resulting in tetanic contraction
With Direct Current what is the effect on Muscle Stimulation?
DC will depolarize the muscle and cause a
single twitch, but only one. To get a tetanic contraction, the muscle must depolarize and repolarize before depolarizing again.
- DC results in a sustained state of depolarization. The muscle cannot repolarize until the DC temporarily ceases.
What is Frequency? What does low frequency and median frequency include?
This is the number of pulses or wave forms per unit of time
- Low Frequency currents currents include TENS and NMES
(Conventional/portable)
-Typically < 1000Hz or 1kHz - Median Frequency currents include Russion and Interferential (IFC)
-Typically 1 to 10kHz
What is Burst Frequency?
The generation of two or more consecutive pulses separated from the next series of consecutive pulses is termed a burst, and the time between bursts is the interburst interval 1. The frequency at which bursts are generated is the burst
frequency, while the frequency of the underlying waveform in the burst is termed the carrier frequency
What is Pulse Amplitude?
Often referred to as intensity, its the magnitude of current or voltage with respect to the isoelectric or baseline on the x-y current-time plot. Amplitude is reported in units of current (amps, milliamps, or microamps) or voltage (volts, millivolts, or
microvolts) and can be described in terms of a single phase or both phases
What is Pulse Duration?
the total time elapsed from the beginning to the end of a single pulse, including the interphase (intrapulse) interval
With Modulation of Pulsed Currents, what is On-Time?
The duration for which a
series of pulses or bursts is
delivered
With Modulation of Pulsed Currents, what is Off-Time?
The duration or time between
a series of pulses or bursts
With Modulations of Pulsed Currents, what is Duty Cycle?
The percentage of the on-time to the total time (on-time plus off-time) multiplied by 100%
Ex:
On Time = 10 sec
Off Time = 40 sec
Duty cycle = 10/50 x 100 = 20%
