Download Chapter 9 (Part A)

Chapter 9. Principles of Electricity for Electrotherapy (Part A)
Basics of Electricity
Electricity Defined - ____ definitions
1. A property of certain fundamental particles of all _____________ that have a
__________ ____________ associated with them, manifested by an
___________________________ of, or __________________ of, _________________
on an atom or body
2. A form of ____________________ associated with the existence and
__________________ of ________________ charge, manifested by the
___________________________ of, or __________________ of, _________________
on an atom or body; exhibits ___________________ (electromagnetic), chemical,
mechanical (electrokinetic), and ________________________ properties
3. A form of energy that exhibits __________________, chemical, mechanical, and
_________________ effects; formed from the interaction of positive (+) and negative (−)
_________________
4. The physical phenomena associated with the existence and ____________________ of
electrical charge, either ________________ charges (electrostatics) or _______________
streams of charge (current)
Electricity
(1) Static Electricity
•Static electricity is ____________________ electricity.
–One body _________________ electrons; the other ________________electrons.
–Stored in an insulated conductor in which the charges are in a state of tension
–State of tension =
(2) Current Electricity
•A stream of loose ______________________ passing along a _____________________
•Current passes in two ways
–_________________ current (DC)
–_________________ current (AC)
DC Current
•Steady _________________ flow of electrons
•Example:
•Also called _________________ current
AC Current
•Flow of electrons that rhythmically _________________ direction
•Two terminals of generator (source) alternatively change from _________________ to
_________________
DC and AC Current Modulation
Most common =
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Physics of Electricity
•Matter
–
•Element
–
•Atom
–
–________________________ part of an element
–Composed of _________________, _________________, _________________, and
other smaller substances
•Molecule
–Two or more atoms held together in
–May be same (____) or different (_____)
•Proton
–
–
•Neutron
–
–
•Electron
–
–
•Electrical charge
–Net sum of charges of _________________ and ____________________
•Difference between number of _________________ and ________________
•In normal state:
•Chemical, mechanical, solar, or thermal force causes _________________ to be
_______________ or ___________________ from the atom, and it becomes
__________________ or __________________ charged
•Ion
•Atom or molecule that has _____________ or _______________ one or more
________________
•Is either _________________ or ___________________ charged
•Electrolyte
•Substance that contains ____________
•Able to ______________ electricity
Current Flow
•Flow of ___________________ _________________ from one point to another
–Higher concentration of _________________ to an area lacking _______________
•Flows from ___________________ pole to ________________ pole
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Conductor
•Substance that can ____________________ _________________ ________________
•Must have ____________ electrons that can be pushed along
•
•_______________ with minerals or electrolytes is a good conductor.
–Good electrical conductors also good ___________ conductors.
•Electrical conductors don't allow electricity to flow ___________
–They oppose the flow of electricity, called ____________________
Conduction
Insulator
•Nonconductor
•________________ the flow of electrons.
•Has no free ___________________ to bump
•Examples
–
Semiconductor
•Substances whose conductivity is ________ at _______ temperatures
•Increases when small amounts of other _________________ are added
–
•__________________ flow of electricity
•Examples
–
Partial conductor
•Substance that allows some flow of electricity under certain conditions
•Examples
–
Quantifying Electricity
•Coulomb
–The basic unit of ____________________
–Produced by 6.28 × 1018 displaced electrons (6,280 quadtrillion)
•Voltage (V)
–Force created by __________________________ of extra _________________ at one
point in circuit, usually corresponding to _________________ of electrons at another
point in circuit
–If two points are __________________, difference in _____________ population
causes __________________ to move from area of _________________ concentration
to area of _____________
–Volt (V) is unit of ______________
–Force required to push a current of 1 amp (A) through a resistance of 1 ohm (Ω)
•Voltage sources
–From ___________________ battery or generator
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–Voltage from a _____________________ is called electromagnetic force (emf)
–Commercial emf either 110 or 220 V
–High-power transmission lines are 20,000 V
•Ampere (A)
–Unit of ________________ _________
–Equal to the passage of one coulomb per second — that is 6.28 × 1018 electrons passing
per second
–Electromedical work requires much less (milliamperes, mA).
–Some therapeutic devices use 0.1 to 1 mA, others use 500 to 1500 mA
•Ohm (Ω)
–Unit of ____________________ or opposition to the flow of _________
–Equal to resistance of a column of mercury 1 mm2 in cross section and 106 cm high at
0°C
–Resistance
•Opposition to flow of ____________ in a _______
•Caused by the _______________
•Determined by:
–
–
–
–
–Impedance
•Opposition (resistance) to flow of _________________ in a _______
Review
Elements of current flow:
•Force =
•Flow =
•Resistance =
Current = Force / Resistance
Water/Electricity Analogy: Water through a pipe similar to electricity through a conductor
•Volume
–Water:
–Electricity:
•Rate of flow
–Water:
–Electricity:
•Resistance to flow
–Water:
–Electricity:
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–Owing to characteristics of the pipe or conductor
•Pipe: narrow or wide, long or short, rough or smooth
•The composition and size of the conductor determine its resistance
•Requirements for flow
–Water
•
•
•Closed system of pipes to carry the water in (if you want to control flow)
•Water flows by displacing _____________
•_________________ or _____________________ to help direct flow
•Different sizes of pipe to provide resistance and help control volume of flow
–Electricity
•
•
•Closed system (circuit) of _________________
•Electricity flows by displacing ___________________, which must be accepted
by something else; must have a complete circuit.
•Different sizes of resistors to provide resistance and control volume of flow
Electrical Equipment
Generator
•A tale of two devices:
–A device that _________________ various forms of energy into
_________ electricity
–A medical device that converts an input electrical current (AC or DC)
into various output currents (AC, DC, or pulsed)
Terminal (pole)
•Output device of a battery or generator
•Attached by wires to ___________________
•Positive
–Terminal from which current _________________ generator
•Negative
–Terminal into which current ________________ to generator
•Electrical circuit
–System of ___________________ that allows __________________ to
move between __________ of a generator
–Closed circuit
•
•
–Open circuit
•
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Medical Devices
•Muscle stimulator (neuromuscular electrical stimulation, NEMS)
–A therapeutic device that delivers current to the body to cause ______________ and
______________ nerve ______________________________
–Causes _______________ _____________________
•Nerve stimulator (transcutaneous electrical nerve stimulator; TENS)
–Therapeutic device that delivers current to the body to cause _________________ nerve
____________________________________
–Stimulate sensory nerves to ___________________ ____________
–Muscle contraction __________ occur, but this is not the purpose of (or necessary for)
TENS stimulation.
Safety Devices
•Circuit breaker
–Safety device that protects equipment and structures from ______________ current
–Manufactured to respond to specific amounts of current flow (such as 10 A, 30 A, etc)
–When current exceeds the specified rating of the breaker, it ___________________
•Ground-fault interrupter (GFI)
–
–Senses very small ______________-_____________ currents that might flow through
the body of a person standing on damp ground while touching a hot AC line wire.
–Acts in a little as 0.025 sec to the circuit breaker
–Typical trip in homes is at ____ mA
–Used chiefly for wall-outlet circuits into which potentially dangerous appliances might
be plugged
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