Concepts Flashcards
kinetic energy
thermal
mechanical
electrical
magnetic
potential energy
chemical
elastic
nuclear
gravitational
conduction
energy transferred when two objects touch
example of conduction modality
heat pack
convection
energy transferred by circulating medium
convection modality example
whirlpool tub
conversion
change in matter state, less heat transfer
conversion modality example
ultrasound turning electrical energy from machine into sound waves
what is an electrical charge?
subatomic particles experiencing force when placed in an electrical field
field made by electromagnetic intersections of particles’ electrons
approximating electrons generates force and generates movement of current
electricity
type of energy that can be stored as potential energy and flow as current when turned into kinetic energy
current
flow of electrons among particles in a circuit/material
why are metals conductive?
they have free electrons that are not tightly bound to each atom so they are easily moved and influenced by current
why is rubber an insulator?
it’s electrons are tightly bound and won’t allow electron movement to generate an electrical charge
principles of electrical charge
opposite charges attract
like charges repel
charges can’t be created or destroyed, only transferred
charges can be transferred object to object
cation
positive ion
anion
negative ion
coulombs law
The interaction between charged objects is a non-contact force that acts over some distance of separation
the forces exchanged by particles depends on how close or far away they are from each other as well as their respective charges and polarities
voltage
difference in electrical potential energy that can be converted to current when particles are approximated
Current
movement of charged particles like electrons moving through a conductor
requirements for there to be a current
needs to be a driving force for particles like a voltage (difference in potential energy)
needs a conductive pathway
difference in electrical potential, meaning one side of the pathway has more electrons than the other side
voltage measures:
how big the dam is (potential energy difference)
ampere measures:
how fast electricity comes out (current/flow of electrons)
ohm measures:
potential for energy to be generated
resistance to current flow
ohm’s law (words)
the current (volume of electrical particles per s) flowing through two points of a conductor is proportional to the voltage (difference in electrical potential energy) between the two points
this flow is limited by resistance between the two points
ohm’s law (equation)
I=V/R
I - current
V - voltage
R - resistance
current through a conductor is decided by the voltage between two points and limited by the amount of resistance between the two points
conductor
accepts electron exchange and allows electrical flow
examples of conductors in body
adipose: poor conductor
muscle and nerves: good conductor
resistance
current flowing through a medium that is opposing it
decreases voltage in a circuit
in series resistors
current goes through each one at a time
in parallel resistors
current goes through all at once
capacitance
ability of conductor or insulator to store electrical charge before an AP occurs
relevant for e stim to determine which fiber you’re stimulating
impedance
opposition to alternating/bidirecctional currents
vs resistance is opposition to one way current
sum of resistive, capacitive, and inductive components of tissue determining current flow
alternating current
creates a sinusoidal wave that goes back and forth on same path
AP threshold in nerve fibers
resting membrane potential is -70, once it reaches -55 mV an AP will fire down the axon
repetitive stimulus will hyperpolarize and threshold is raised
rheobase
minimum amount of stimulus intensity over time needed to initiate a response or AP in a fiber
chronaxie
minimum amount of time or pulse duration needed to excite a fiber when the current is 2x the rheobase, or min stimulus intensity to get AP response
microcurrent
doesn’t meet threshold of sensory nerves but may still have effect on ionic movement
