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Chem/Physics (Exams 2 and on) > Electricity and OR Electrical safety > Flashcards

Electricity and OR Electrical safety Flashcards

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1
Q

What is current?

A

the flow of electrons

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2
Q

What is capacitance?

A

stored charge is discharged from defibrillator

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3
Q

What is Ohm’s Law?

A

I= V/R
where V= voltage= electromotive force= potential difference
I= current- quantity of electrons measured in Amperes
R= resistance-force in opposition to flow of electrons measured in Ohms
analogous to Q= P/R

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4
Q

What is electric current?

A

how much charge (how many electrons) pass a certain point in a circuit per unit time

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5
Q

What is a Coulomb?

A

a unit of measure of electric charge

just like “gram” is a unit of measure of mass

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6
Q

How many electrons are needed to generate 1 Coulomb?

A

6.24 x 10^18 electrons carry a charge of 1 Coulomb

Each electron has a charge of 1.60 x 10^-19

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7
Q

1 ampere is

A

the movement of charge carried by 6.24x10^18 electrons passing a certain point in 1 sec
or 1 Ampere of current the movement of 1 Coulomb of electric charge passing a certain point in 1 sec

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8
Q

In order to have flow, there must be

A

a complete circuit

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9
Q

Voltage is lost as

A

electrons move through area of resistance

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10
Q

What is impedence?

A

resistance to current flow that changes with frequency
consists of resistance plus other factors that effect electron flow
how resistance changes with changes in frequency

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11
Q

A watt is

A

the unit of power (work done/unit time)

the product of voltage and current

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12
Q

A watt-second is

A

work or energy

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13
Q

How is energy measured in a home versus in a defibrillator?

A

defibrillator- Watt-sec

home- Kilowatt-hours

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14
Q

Power is equal to

A

current x voltage

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15
Q

A closed loop must have:

A

driving pressure (voltage) to force a current (ampheres) to flow through a Resistance in accordance with Ohm’s Law

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16
Q

What is the current if the voltage is 120 and the resistance is 240 ohms?

A

current is 0.5 amps

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17
Q

A conductor is

A

any substance that permits a flow of electrons
I.e. metals & human tissue
substance has loosely attached and easily lost electrons which permits flow electrons

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18
Q

A nonconductor or insulator

A

have tightly bound electrons which do not permit electron flow
include: glass, rubber, plastic, dry wood, pure water

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19
Q

What is a direct current versus an alternating current?

A

a direct current (DC, batteries)- the electron flow is always in the same direction
an alternating current (AC, electric company)- the electron flow reverses direction (Oscillates) at regular intervals
the oscillating frequency is measured in cycles per second or Hertz

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20
Q

How many cycles of electrons (wavelength) can we get in 60 seconds?

A

60 Hertz (US)

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21
Q

What is capacitance and a capacitor?

A

a measure of a substance’s ability to store a charge

a capacitor is an electrical device used for storing electric charge

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22
Q

How does capacitance work?

A

it consists of 2 parallel conductors separated by an insulator (non-conductor)
can be AC or DC circuits

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23
Q

Insulated wires running next to each other will produce capacitance

A

simply by being plugged in even though the equipment is NOT turned on

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24
Q

The strength of the electric field is much greater when

A

there is more coiled wire which allows more atoms to be oriented–> stronger magnet

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25
Q

Having an iron core with coil wrapped around

A

produces a much stronger magnet than with the coil alone (has more atoms and thus generates more electric field)

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26
Q

Electrons flow from

A

negative to positive

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27
Q

The electromagnetic field can

A

do work; it can push and pull magnets and push and pull electrons

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28
Q

Electromagnetic fields can influence

A

other circuits in close proximity
a circuit where electrons are flowing generates a magnetic field that pulls or pushes electrons that are nearby (and can easily be pushed and pulled) and this generates a second current

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29
Q

If the wire is coiled repeatedly around an iron core

A

the magnetic field induced can be very powerful

30
Q

In an AC circuit, inductance can electromagnetically

A

generate an opposing electromotive force (current in a nearby wire)

31
Q

A motor is

A

when we have a fixed magnet and rotating metal bar
the electric fields from the magnet are repelling the electric field from the wire
allows us to use repulsion between two sources of electromagnetic fields that oppose one another to do work

32
Q

A generator works by

A

have rotating magnets and a fixed bar; the electromagnetic fields are sufficient to move electrons through inductance which generates an electric current

33
Q

High impedance results in

A

low current flow

34
Q

Low impedance results in

A

high current flow

35
Q

Utility companies supply electrical energy in the form of

A

AC current of 120 V and 60 Hz

36
Q

To have a current flow, there must be a complete circuit with

A

a voltage source to drive the current through the resistance

37
Q

A short circuit or fault is defined by

A

a condition in which there is ZERO impedance with a high current flow

38
Q

A power cord consists of 2 conductors:

A

“Hot” conductor returns the current through the impedance
“Neutral” conductor returns the current to the source
the potential difference between the 2 conductors is 120 V

39
Q

A person can be shocked by

A

touching a wire directly or touching a conductor that is touching a wire

40
Q

Grounding equipment is

A

a way to prevent someone from being part of the circuit by attaching a metal wire from the device to the ground

41
Q

Electric shock can occur by

A

contacting AC or DC current (takes about 3x DC as AC to cause vfib)

42
Q

A person must contact the electric circuit at

A

2 points and there must be a voltage source causing current to flow in order to be shocked

43
Q

What is a macroshock?

A

large amount of current flow through a person

44
Q

What is a microshock?

A

very small amount of current flow through a person (Conditions: external conductor in direct contact with the heart such as a PA catheter) much smaller current would be needed to cause vfib in this situation because it has a direct line to the heart

45
Q

The severity of the shock depends on:

A

the amount of current (Amperes) and the duration of contact

46
Q

If an individual contacts an external source of electricity damage can be produced in 2 ways:

A

current can disrupt normal electrical function of cells

current passing through a resistance (the body) raises the temperature of the substance and can produce a burn

47
Q

At 100-300 mA

A

ventricular fibrillation will start, but respiratory center remains intact

48
Q

The recommended maximum allowable 60-Hz leakage current is

A

10 microamperes

49
Q

100 microamperes can cause

A

ventricular fibrillation if in direct contact with the heart such as a PA catheter

50
Q

If there is any buildup of charge on a device that is grounded

A

the grounding element allows the charge to go down to the ground and be discharged

51
Q

In the OR, our source is

A

not grounded but our equipment is

52
Q

Grounding can be used to describe several different principles:

A

the grounding of the primary electrical power supply

the grounding of electrical equipment itself

53
Q

Faulty equipment in the OR does

A

not present a shock hazard when plugged into an isolated power system

54
Q

In the OR, even though the power system is isolated from the ground,

A

the equipment case is still connected to an equipment ground

55
Q

All AC power systems and electrical devices

A

manifest some degree of capacitance

56
Q

There is a small amount of ________ ________ to the ground with our devices in the OR

A

“Leakage” current

The OR system is set to alarm for anything above 5 mA which may indicate a short circuit

57
Q

The electrically susceptible patient is

A

a patient with a direct external connection to the heart such as a PA catheter

58
Q

The electrically susceptible patient is protected against microshock

A

by an intact ground wire
-if the equipment ground wire is broken all 100 microamps of leakage current could flow through the catheter causing v-fib

59
Q

The Bovie or electrosurgical unit operates by

A

generating very high-frequency AC currents of anywhere from 500,000 to 1 million Hz
produces voltage as high as 3000 V
Produces close to 400 watts of power

60
Q

Heat is generated whenever a current passes through

A

resistance

61
Q

The amount of heat produced is

A

directly proportional to the square of the current and inversely proportional to the area through which the current passes

62
Q

The heat formula for ESU:

A

H= I^2 x A

63
Q

High frequency currents have

A

low tissue penetration and do not excite contractile cells and therefore do not cause V-fib

64
Q

The current for the Bovie must

A

enter the patient and be routed back to the ESU through using a return plate
Energy passes through the patient to the return plate with a large surface area that returns it safely to the ESU

65
Q

A properly applied return plate

A

covers a large surface area. No harmful heat is generated and no tissue damage

66
Q

The placement of the return plate needs to be

A

close to operative site
as far away as possible from EKG pads
ensure adequate gel and sufficient skin contact
not placed over scar tissue, hair, or implants

67
Q

The dispersive plate must cover

A

a large area so that the current density is below a level that will cause burns

68
Q

The current will seek to return to the ESU through alternate conductors if:

A

the dispersive plate is not properly applied to the patient
return plate is dislodged during the procedure
return plate cord is damaged or not properly connected
insufficient conductive gel

69
Q

Alternate conductors of current include

A

anything attached to the patient such as ECG leads/temperature probe

70
Q

What are the types of ESU units?

A

unipolar- current returns to unit via dispersive pad
bipolar: two electrodes that look like forceps-dispersive pad is not necessary and less energy than unipolar
Argon beam coagulator (unipolar)-uses a stream of argon gas to support the electric current

Chem/Physics (Exams 2 and on) (9 decks)

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