ANES 501 Lecture 4: Electricity & Electrical Safety MASTERY GUIDE 2025 – Expert-Curated Q&A with Detailed Rationales, Operating Room Safety Protocols, and Equipment Hazard Prevention

Ohm's law =

E = IR

E = voltage

I = amperage

R = resistance

Power =

watts = E x I

Electrical work =

watts x seconds

joules

If electron flow is always in the same direction the current is

DC (direct)

If electron flow reverses at regular intervals the current is

AC (alternating)

Impedance (Z) is

the resistive force in an AC circuit

Z =

frequency x inductance

Z = 1 / frequency x capacitance

capacitance

The greater the frequency the less the impedance

inductance

an opposing force can be induced in a separate wire or iron core

In order for a device to be powered ______________ must be completed

an electrical circuit

If the circuit is broken at any point what will happen

the circuit will no longer be powered

_____________ is grounded

power

What is the zero-resistance conductor

the earth because of the metallic content of the earth's crust and core

How does power enter hte home

via 2 lines

Hot and neutral

which line is grounded (hot or neutral)

neutral

Once power enters the home where does it go

circuit breakers

circuit breakers are usually

15-20 A

Do circuit breakers protect from lethal shock

no

in a grounded system flow ill

be between the hot wire and any conductor with the ground

What happens when you come in contact with a "hot" wire

An electric shock will be produced because we are nearly always grounded

AC has a propensity for causing what heart dysrythmia

V fib

How much AC power is required compared to DC

1/3 the amount of DC

In the USA power is supplied as how many V at how many Hz

120 V

60 Hz

electrical shock occurs when

a person completes an electrical circuit

What 2 ways can tissue damage occur

1- disruption of normal cellular electrical activity

2- thermal injury

macroshock refers to

a large amount of current flow (in excess of 5 mA)

60 Hz 120 V for 1 second duration has a

1 mA threshold of perception

10-20 mA is the __________ current

let go current

50 mA causes

pain

100-300 mA will cause

V fib

6000 mA will cause

extensive tissue damage

Current density refers to

current applied per unit area

In the OR power is

ungrounded

how is OR power accomplished

with an isolation transformer

What does it mean if power is ungrounded

neither wire is hot or neutral relative to the ground

With ungrounded power equipment casings will be

grounded to allow discharge of leakage current

why is leakage current formed in AC circuits

because of capacitance/inductance

The line isolation monitor monitors

the integrity of an isolated power system

What 3 things does the line isolation measure

measures circuit impedance to ground

What does the line isolation monitor indicate in milliamps

the total possible current flow to ground

What is the isolation monitor alarm set between

2-5 mA

What 2 conditions will cause the isolation monitor to alarm?

1- faulty piece of equipment, allows more than 5 mA to go to ground

2- 2-5 mA is reached in the system w/ leakage current

What will cause a 2-5 mA of leakage current & cause the line isolation alarm to go off

occurs from the sum of small leakage currents from multiple pieces of equipment reaching the alarm threshold

The equipment ground wire allows for

disbursement of the leakage current

(the line isolation monitor cannot find a break in the grounding wire)

What does the ground fault circuit interrupter (GFCI) monitor

the current in the hot and neutral wires

When will the GFCI interrupt the circuit

if there is a difference of > 5 MA in the circuit

Microshock

a catheter or wire in the heart that can deliver a very high current density

How many microamps may induce V fib

as little as 100 microamps

Presently used patient moniots will isolate what

the power supply from the patient with very high impedance

can deliver < 10 microamps

what is the recommended upper limit of leakage current

10 microamps

Do circuit breakers, isolation transformer, and line isolation monitors protect from microshock?

NO

Electrosuurgery uses what frequencies (range)

high

500,000 = 1,000,000 Hz

The heat produced in electrosurgery is inversely proportional to

the area delivered

High frequency of electrosurgery ________________ induce V-fib

does not

(0.2-2 mHz)

In electrosurgery the large return pad causes

diffusion of current

In electrosurgery because of high frequency what type of current will be induced

induced current is high

possiblity of patient conduction of current is great

Electrosurgical devices can cause problems with these 2 devices

pacemakers

AICD's

Which type of device is preferable and can cuase less induction

bipolar

if using a unipolar device it should be used.... (3 things)

1- with the lowest possible settings

2- for as brief a period as possible

3-not used w/ in 15 cm of a pacemaker or AICD