Week 8 - Electrical and Fire Safety in OR Flashcards
What is Coulomb’s law?
Like charges repel each other while opposites attract
Electricity results from _________ __________
mobile charges
Electrical charge is measured in ____________ and a e (electron) has a magnitude of ___________
Coulombs, - 1.602^-19 C
How does electricity flow?
Movement of electrons from an area of high concentration to and area of low concentration
Stationary electrical charges vs electrical potential
Different!
SEC –> Measured in Joules, holding energy “still” (Cardioversion)
EP –> Measured in Volts, Volts = Joules / Coulombs
What is Ohm’s Law?
The potential of flow of electricity is proportional to the actual current, AFTER accounting for resistance
Measures resistance → V (potential difference) = I (current) x R (resistance). V = IR
What are good conductors of electricity?
Good conductors → Allow electrons to freely move through material with LITTLE resistance → Copper, METALS are generally good conductors. Exception → Graphite which is a non metal but conducts electricity fairly well
Metals are good conductors because their outer electron shells are mostly empty, allowing for electrons to freely flow through with little resistance
What are good insulators of electricity?
Good insulators → RESIST flow of electrons, they cannot freely move around → NON-METALS, can be charged, Silicon
Resistance → All materials offer some level of resistance, even conductors. The energy required to push electrons through a material is a measure of the resistance of the material
What is resistance in electricity?
Resistance is simply a ratio of voltage to current → How hard is it pushing to move these electrons. R = V / I
Materials that obey Ohm’s law are termed?
Materials that obey are termed ohmic, materials that do not (which there are a lot) are termed non-ohmic (diodes)
How does the ground play a role in electrical flow?
Ground is a conductor, connected to the earth’s ground → provides an alternate path for electricity to flow in a power surge
What is a DC circuit?
DC circuit → Electricity ALWAYS flows in one direction, generally how battery powered devices function (flashlight)
What is the Law of Conservation of Electrical Charge?
The total amount of electrical charge in the universe is constant!
Charge is simply transferred
Charges that move are _________
negatively charged
Coulomb’s law can be used to calculate what?
The force or attraction or repulsion between two charges
All electrical charges posses a force field, what is this?
This is what exerts the electrical force on a test charge located at any point around a central charge
This is a vector → SI units are Newtons per Coulomb (N/C)
An electrical current is _______ and is measured in __________
Moving electrons (negatively charged), amperes (amps).
This is the amount of charge flowing per unit of time –> 1 amp = coulombs / time (seconds)
What is an electrical circuit?
A circuit exists when a charge is able to flow through a closed path
2 types –> DC and AC circuits
What is an AC circuit?
Current can periodically change direction
Derive their energy from wall outlets or AC generators
What is a series circuit?
One pathway for current flow, voltages and resistances are additive
3 2 V batteries = 6 V
Car batteries work this way → 12 V battery from 6 2-V batteries
Resistors work by adding sum together as well
50 ohms and 25 ohms resistors = 75 ohms
What is a parallel circuit?
Current has more than one path it can take and resistors are connected in each pathway (household circuits)
Allows for electricity to run through separate circuits → Can turn on the microwave without everything else turning on
Each current runs through a resistor independently → Total resistance is found by adding inversely
Real circuits consist of both parallel and series circuits
What is electrical power?
Power is the rate at which energy is expended or consumed. P = I x V → Watts = amps x volts
Current x Potential energy
What is electrical energy?
Power x Time
Kilowatt hour is generally the unit used
What are the two types of semi-conductors?
P-type (positive type) → Silicon doped in boron. Boron atoms have one less valence electron than silicon atoms. More “positive holes”
N-type (negative type) → Silicon doped in arsenic. Arsenic atoms have one additional valence electron compared to silicon atoms.
What are semiconductors primarily made of?
Silicon, semiconductors are primarily used in computers
What are triodes?
Triodes → Known as transistors. Made from two closely situated pn junctions. Used for amplifying or switching currents
Two examples of where spectroscopy is used
Used for analysis of blood work and a pulse oximeter
What is spectroscopy?
The study of the absorption and emission of light and other radiation by matter
When white light passes through a colored substance, certain wavelengths are absorbed
In regard to spectroscopy, a substance __________ its _____________ color
absorbs, complementary
Ex –> Red things absorb green light
What is a monochromator?
Essentially a prism, a beam of light passes through and directs the light through a second silt before hitting the sample and then detector
How are spectrometers designed?
Spectrometers have the same basic design
Source of light goes through a silt to monochromator → this goes through the 2nd silt and then to the sample. Finally, the detector measures the intensity of the light
The source emits the desired wavelength of electromagnetic radiation.
What is this definition referring to in regard to spectroscopy?
Instrumentation
What is Beer’s law?
How light is absorbed by the sample (blood)
(A = abc)
What 3 things affect Beer’s law?
Absorptivity → Should be between 0.1 and 1 (a)
Increasing the Distance (b)
Concentration of the analyte (c)
What is transmittance in relation to Beer’s Law?
Fraction of light passing through a sample. Influenced by intensity of the light
The strength of a shock depends on what three things?
- Path of the current
- Magnitude of the current
- Duration of the contact
What two things can complete a path through which a current can flow?
Stray capacitances and Inductances
Macroshock is when _________
A relatively large amount of current flows through the body potentially resulting in injury or death
100 mA can initiate ventricular fibrillation
Microshock is when _________
A relatively small current is delivered externally directly to the heart via a low resistance pathway
100 microAmps or less can initiate ventricular fibrillation (book says 50 or less)
The longer an individual is in contact with a current, ____________
the greater the damage
How does a fuse work? What happens when this is burned out?
Fuses → If the current exceeds the rated value, the fuse will melt preventing further current from flowing
Needs to be replaced after burned out
What is the purpose of fuses and circuit breakers?
Designed to limit current flow in the event of a short circuit or circuit overload
How does a circuit breaker work?
Bimetallic strip → Will warp when heated too much which opens or “trips” the circuit. Once the strip cools it will return to its original shape allowing current to flow → The circuit will need to be reset with the flip of a switch.
What are three modern safety devices to help prevent circuit overload or a short?
Polarized plugs, three-pronged grounded plugs, and ground fault circuit interrupters (GFCIs)
What is a polarized plug?
One wide and one narrow prong → Narrow = high potential, wide = low potential
Casing is connected to the wide prong or low potential, this isolates the device case from the high potential
How does a three pronged grounded plug work?
The third prong provides a path to divert the high potential current directly to the ground thus protecting someone from touching the case of the appliance.
This is IF a high potential wire comes in contact with the appliance casing
How does a three pronged grounded plug look?
Two equal flat plugs with a third rounded ground prong wired directly to the case of the electrical device
Where would you expect to see a ground fault circuit interrupter?
A protective outlet used near water sources (sinks, tubs, and pools)
How does a ground fault circuit interrupter work?
Detects current imbalances between a high potential wire and a low potential wire
In a ground fault circuit interrupter, should the low and high potential wires be equal in current?
Yes
Designed to immediately shut off if there is an imbalance between the two currents
High potential and low potential wires should equal each other in current flow IF working correctly.
At what current difference does a ground fault circuit interrupter “trip”?
5 mA
What does a ground fault circuit interrupter look like?
Has two additional buttons on a normal looking outlet.
One button works to test the functionality
Second button is used to reset the circuit
Ground fault circuit interrupter placed upstream from additional outlets can do what?
Can protect the outlets downstream from the GFCI even though they are “normal” looking outlets
For circuit containing more than one outlet, this GFCI outlet can be placed at the first receptacle while the other outlets are “regular” but still protected by this outlet
Can also be placed in a circuit breaker with subsequent outlets looking regular but protected by this.
What type of system is primarily used in the OR?
Ungrounded systems
Why are ungrounded systems preferred in the OR?
Benefits are that when standing on the ground and touching a high potential wire, you won’t complete the circuit and receive a shock → Will receive a shock however if you touch TWO wires simultaneously
Why is there a high risk of macroshock in the OR?
Abundant electrical devices and conducting fluids (electrolytes)
What is an isolation transformer?
Works through electromagnetic induction
Outsources the secondary circuit (ungrounded) via an isolation transformer, which doesn’t physically touch the current, to the primary circuit (grounded) OUTSIDE of the OR
What is Faraday’s law of induction?
Faraday’s law of induction → Changing magnetic flux in one coil produces a changing voltage, and hence a changing current in the second coil.
What additional safety feature is used in the OR in ungrounded systems?
Line isolation monitors (LIMs)