Electricity And Electrical Safety Flashcards
What is electricity?
Effects produced by moving charges
What are two kinds of charge?
- positive
- negative
What is the SI unit of charge?
Coulomb (C)
Charge of 1 electron
-1.6 x 10 ^ -19 C
“-e”
Charge of 1 proton
+ 1.6 x 10 ^ -19 C
“e”
Opposite charges
Attract
Like charges
Repel
Coulomb’s Law
Like charges repel, opposite charges attract
Law gives the magnitude of the electrostatic force of attraction or repulsion
What is electric current?
The amount of charge flowing per unit time
Conductors
Materials in which charges can easily move
___ are good electrical conductors
Metals
Most ___ are nonmetals and generally are not good conductors
Insulators (except for graphite)
To be a good conductor, electrons must be able to…
Move easily from one atom to the next
Electrical conductors are made of atoms that ___
Do not hold onto electrons tightly
Metals have electron shells that are mostly ___
Empty—good conductors
I.e.: Copper only has one electron in its fourth energy level
In the molecular orbital (MO) approach to bonding, atomic orbitals from individual atoms are ___ together to form molecular orbitals that extend over the entire molecule
Added
The MO approach to bonding results in a large collection (or band) of MOs that is only ___ filled; thus, there is room to ___ into the “molecule” with very little energy
Partially filled; room to accept new electrons
Electrical conductors allow electrons to pass through their conduction bands with very little effort, but not ___ effort
Zero
The energy required to push electrons through a material is a measure of the ___ of the material to the passage of current
Resistance
Resistance is measured in ___
Ohms
Conductance is the reciprocal of ___
Resistance
Conductance is measured in ___ or ___
Mhos or Siemens (S)
What is the electric circuit?
The closed path through which a charge flows
Direct current (DC) circuit
An electrical circuit in which the current flows in one direction only
Alternating current (AC) circuit
An electrical circuit in which the current reverses its direction in a periodic fashion
DC = electron flow is always ___
In the same direction
AC = electron flow ___ at regular intervals
Reverses direction
Short circuit
A situation in a circuit where the normal resistance of the circuit is bypassed by a low resistance path, resulting in a large current
If the current from a short circuit is not limited by a fuse or circuit breaker, the resulting heat from the high current can lead to a ___
Fire
Series circuits—when batteries or resistors are connected in a series, the voltages and resistances are ___
Added
Parallel circuits—when resistors are connected in parallel, current flows through each resistor ___ of the other
Independently
Electrical power is the product of ___ and ___
Volts and amps
Power is measured in ___
Watts
Power is the ___
Rate of using energy
Power =
Energy/time
Energy =
Power x time
Two types of electrical shocks:
- Macroshock
- Microshock
Macroshock
Large amounts of current conducted through a patient’s skin or other tissues
The extent of injury will depend on the amount of current and the duration of the exposure
Microshock
The delivery of small amounts of current directly to the heart
Very small currents (< 50 micro amps) can produce ventricular fibrillation!
What is on a piece of equipment that provides a low-resistance pathway for leakage current and constitutes the major source of protection against Microshock in the electrically susceptible patient?
The ground wire
Never simultaneously touch an electrical device and a ___ or ___
Saline-filled CVP catheter or external pacing wires (wear rubber gloves)
Polarized plugs
Plugs with one narrow prong and one wide prong
Polarized plugs ensure that the plug may only be inserted into the outlet in ___
One orientations
Narrow prong is for ___
High potential
Wide prong is for ___
Low potential
Electrical devices are designed so that the casing is connected to the ___ and thus at low potential
Wide prong
Three-pronged grounded plug
Plug that contains a rounded third prong that is connected to ground when plugged into a three-pronged receptacle
The third prong is wired directly to the ___
Casing of the electrical device
If for some reason a high-potential wire comes into contact with the case, the current will flow directly through the ___ instead of through your body
Third prong
Ground fault circuit interrupter (GFCI)
Immediately (within 1 ms) disrupt the flow of current in the circuit if a change in current is detected
GFCIs are used in circuits near ___
Water sources
What is a disadvantage of using a GFCI in the operating room?
It interrupts the power without warning—the defective piece of equipment can no longer be used, which might be a problem if it were necessary for life support
Modern electrical circuits are typically ___
Grounded (intended as a safety feature but can pose a risk to humans)
How can shock to a human occur at ground potential?
Humans who are at ground potential because of what they are touching have to only touch a single object to complete a circuit, resulting in shock
To further decrease the risk of electrical shock in operating rooms, electrical systems are isolated from the ___ through the use of isolation transformers
Grounded electrical supply
Isolation transformers rely on ___ to transfer a current from the grounded electrical system to an ungrounded secondary system without the two systems ___
magnetic inductance; WITHOUT the two systems physically contacting each other
Ungrounded systems in the operating room prevent ___
Accidental shocks resulting from simply touching a single live wire
If live wires make contact with a ground, the ungrounded system now becomes a ___—we thus say that a ___ has occurred, resulting in a ___
Grounded system—a fault has occurred, resulting in a grounded system
A fault can occur if a live wire touches a ___
Casing on a piece of equipment
A second fault can result in a ___
Shock
What is a line isolation monitor?
A device that alarms when a fault in an ungrounded system occurs
Line isolation monitors are located between ___ and ___ so that the impedance to current flow can be measured
Live wires and a ground
If contact is made between a live wire and a ground, current will flow, resulting in ___
An alarm
The alarm set point for a line isolation monitor is usually between ___ and ___ mA
2 and 5 mA
If the gauge on the line isolation monitor reads between 2 and 5 mA, there is probably ___ plugged into the circuit
Too much electrical equipment
If the gauge is reading > 5 mA, it is likely that a ___ is present in the operating room
Faulty piece of equipment
Equipment may be identified by unplugging each piece of equipment until the alarm is silenced
If faulty piece of equipment is not essential, it should be removed from the operating room
The line isolation monitor is not designed to provide protection from ___
Microshock
Potential hazards in the operating room include ___
Electrical shock to the patient and operating room personnel
All healthcare facilities are required to have ___
A source of emergency power (electrical generators, battery-operated light sources including laryngoscopes, etc.)
Objective of electrical safety is to make it difficult for ___
Electrical current to pass through people
Isolation transformer is used to convert ___ power to ___ power
Grounded power to ungrounded power
Line isolation monitor warns that ___ has been lost in the event that a defective piece of equipment has been plugged into one of the isolated circuit outlets
Isolation of the power from the ground has been lost
Equipment that is plugged into the isolated power system has an equipment ___ that provides an alternative low-resistance pathway
Ground wire
Electrosurgery (ESU) operates by generating ___
High-frequency currents (radiofrequency range)
ESU— ___ is generated whenever a current passes through resistance
Heat
High-frequency currents have a low ___ and do not excite ___
Low tissue penetration; do not excite contractile cells
High-frequency electrical energy generated by the ESU interferes with signals from ___
Physiologic monitors
How can the ESU be safely operated?
Application of a large surface area dispersive electrode to the patient (allows energy to be routed from the unit, through the patient, and back to the unit)
ESU—the area of the return plate is ___
Large
ESU—the current density is ___
Low
ESU—no harmful ___ or ___ occurs
Heat or tissue destruction occurs
If the return plate is improperly applied to the patient or if the cord connecting the return plate to the ESU is broken, the high-frequency electrical current will ___
Seek an alternate return path
The power supply is isolated from the ground to protect the patient from ___ by eliminating ___
Burns, eliminating alternate return pathways
The most important factor in preventing patient burns from the ESU is ___
Proper application of your return plate!
