Mod 15: Electrical Safety

What is Coulomb’s Law?

like charges repel each other and opposite charges attract each other.

What can Coulomb’s Law describe?

the electrostatic force of attraction and repulsion

What does electricity require to flow?

a complete circuit

What are the components of a simple circuit?

• positive/hot/live side

• negative/neutral side

• Ground: a conductor connected to earth that provides a low resistance alternative route for electricity in case of electrical surge

What is grounding?

a conductor connected to the earth that provides a low resistance alternative route for electricity in case of electrical surge

what is electricity?

the change in potential energy caused by the movement of electrons from an area of high concentration to low concentration

What is “e” ?

the fundamental unit of charge

What does e equal?

the energy of ONE electron

What is a coulomb?

electrical charge expressed in a more manageable way since electrons are small

1 coulomb = …

6.24 × 10¹⁸ electrical charges

What is the SI unit for electrical charge?

Coulomb

What is volt?

unit for electrical potential energy

What does volt represent?

electrical “pressure” or the gradient of charges that could potentially flow.

What is Volt the SI unit for?

1 J/C

Volts are useless unless…

there is a circuit/path to flow

What is current measured in?

Amperes (A) or amps

1 amp = …

1 C/sec

What can joules represent?

all kinds of energy

What does current bring to the equation?

time relative to a coulomb

What is an electrical current defined as?

the rate of flow of an electrical charge (electrons) through a conductor

How is electrical current expressed in an equation?

I (capital i)

What is a conductor?

any substance that permits the flow of electrons

A good conductor has …

low resistance to flow

What is an insulator?

a material that resist the flow of electricity

When an insulator is present, what happens to the electrons?

they do not move easily

What are insulators also called?

dielectrics (you don’t die if you have an insulator)

What the common conductor in OR equipment?

copper

What does Ohm’s Law measure?

the resistance to electrical flow

What is the formula for Ohm’s Law?

• E = I x R

• voltage = current x resistance

Define the variables of the Ohm’s Law equation.

• E = electromotive force (in volts)

• I = current (in amperes)

• R = resistance (in Ohms)

In Ohm’s Law, the potential …

flow of electric charge is proportional to actual current, after accounting for resistance.

What is Ohm’s Law the basis for relative to anesthesia?

• the equation BP = CO x SVR

• BP = vascular system in voltage

• CO = current

• SVR = forces opposing the flow of electrons

What is electrical power measured in?

watts (W)

How do you designate electrical power in an equation?

P

What is the formula for power?

• P = E x I

• Power = voltage (E) times current (I)

What is a joule?

• the amount of electrical work done measured in watts times a unit of time

• Joule = watt-second

A joule equals …

designation for electrical energy expended in doing work

How can joules be applied to anesthesia?

ACLS and defibrillation

How many joules is biphasic defib?

120-200J

How many joules is monophasic defib?

360J

How many joules if cardioversion?

50J

What does power measure?

work done

What can power also measure in an electrical circuit?

the amount of heat produced by an electrical circuit

Can the formula for Ohm’s law be incorporated for the equation of power?

yes

How do you incorporate Ohm’s law into power?

Ohms: E = IxR

Power = ExI

plug in → P = (IxR) x I → I²xR

What is I² in the equation for power?

the amperage or strength of an electric current in amperes

What is required to calculate the number of amperes and the resistance of a given device?

wattage and voltage

E is …

voltage

I is …

amps

R is …

resistance/Ohms

P is …

wattage

What is current supplied with?

direct or alternating current

Direct and Alternating current can both be …

pulses or continuous in nature

What is direct current (DC)?

electron flow if always in the same direction

Ohm’s Law is accurate when …

applied to DC circuits

What is alternating current?

the electron flow reverses direction at a regular/set interval

1 Hz = …

1 cycle per period

Can Ohm’s law be directly applied to AC?

no

What are AC circuits current opposed by?

impedance

What the amount of Hertz in the US.

60

What kind of power does the anesthesia equipment operate on?

AC

What is impedance?

the sum of the forces that oppose electron movement in an AC circuit

What is impedance designated as in an equation?

Z

What does the opposition of impedance include?

• resistance (ohms)

• capacitance

• inductance

also known as RIC

What is an insulator?

substance that opposes the flow of electrons

What kind of impedance does an insulator have?

high

What kind of impedance does a metal have?

low

What are the 2 components of impedance?

capacitance and inductance

What is capacitance?

the measure of that substance’s ability to store charge

What does a capacitor consist of?

any two parallel conductors that are separated by an insulator

What ability does the capacitor have?

to store charge

When are capacitors useful?

in application in electronic devices

What do capacitors have the ability to leak?

stray capacitance

Is stray capacitance bad?

yeah, you can get shocked

true or false. there are absolute insulators available.

false, there are none

What may stray capacitance create?

an unintended charge in the casing of electrical equipment (NO absolute insulators)

What is inductance?

a property of AC circuits in which an opposing EMF can be electromagnetically generated in the circuit

the net effect of inductance is to …

increase impedance

What will increases in frequency do to total impedance?

increase it

Stray capacitance and inductance may contribute …

a low risk for shock because they are low current flows

What does direct contact of exposed electrical wire do?

constitute a greater risk of electric shock b/c of higher voltages

What are the 3 mechanisms that contribute to the risk of shock?

1. direct wire contact

2. inductance

3. stray capacitance

Why will direct wire contact shock someone?

b/c of insulation damage or faulty construction

How will inductance contribute to a shock?

d/t to the flowing alternating current’s magnetic field, producing a small electrical flow in the surrounding metal casing despite no direct contact

How does stray capacitance cause electrical shock?

from build-up of electrical potentials with an alternating current circuit despite no closed circuit electrical flow

What happens to a person if they make contact with both a live wire and ground?

they may complete an electric circuit and receive a shock.

What is the severity of an electrical shock determined by?

the amount of current (number of amperes) and the duration of flow!!!

What are the 2 categories of electrical shock?

1. macroshock

2. microshock

What is macroshock?

a large amount of current flowing through a person’s skin and other tissues → cause harm or death

Electric current seeks …

the path of least resistance

Electrical current is often dissipated …

throughout the body tissues

in macroshock, is the electrical current enough to reach the heart and cause arrythmia?

no

What is microshock?

the delivery of small amounts of current directly to the heart

What is an electrically susceptible patient?

a person who has an external conduit that is in direct contact with the heart is at risk for microshock

What are examples of external direct conduits to the heart?

CVL/ PA catheter, or PM

Small amounts of current (microshocks) affects who and does what?

electrically susceptible patient and causes v. fib

What is the unit for macroshock?

mA

what is the unit for microshock?

µA

What are the two ways electrical shock can cause damage?

1. disrupt the normal electrical function of cells

2. raise temperature

What are signs of disrupted normal electrical cell funtion?

• contract muscles

• alter brain function

• paralyze respiration

• disrupt heart fx → v-fib