Electrical Safety Practice Flashcards

Comprehensive practice flashcards covering Electrical Safety I, focusing on static electricity, AC hazards, safety devices like fuses and GFI, and clinical microshock hazards.

Why are electrostatic effects more prominent in dry conditions compared to humid conditions?

Moisture in the air can drain away excess charge through attachment to the water molecules.

What is the primary physical hazard associated with the build-up of static electricity?

'Sparking' during discharge.

Why is static electricity sparking particularly dangerous in operating theatres?

It poses a risk in the presence of flammable gases like oxygen or anaesthetic gases.

What precaution involving surgical gowns helps manage static electricity?

Surgical gowns should be treated with silicone.

Which clothing material is recommended to prevent static build-up in sensitive areas?

Natural materials such as cotton.

Which type of flooring is used in operating theatres to handle static electricity?

Anti-static flooring.

In which medical components is anti-static rubber used?

Masks, tubing, trolley wheels, stool seats, boots, etc.

What must someone likely to pose a static discharge threat do before entering oxygen tents?

They should discharge themselves.

What should be done to all electrotherapy or ICU equipment to handle electrical safety?

They should be properly earthed.

What are the three terminals found in most domestic electrical supplies?

Live, Neutral, and Earth.

Between which two terminals is the potential difference (voltage) applied?

Between the live and neutral terminals.

What is the mains electric supply frequency in the UK, Ireland, Bahrain, or Malaysia?

$$50\,\text{Hz}$$

What is the mains supply voltage in the UK, Ireland, Bahrain, or Malaysia?

$$220/240\,\text{V}$$

What is the mains electric supply frequency in the US?

$$60\,\text{Hz}$$

What is the mains supply voltage in the US?

$$110\,\text{V}$$

To what part of an appliance is the earth terminal usually connected?

The casing of the appliance.

What occurs if a person accidentally touches a live wire?

They provide a closed link to earth and current flows through them.

Define a 'short circuit' in the context of electrical appliances.

A breakdown in insulation between the live wire and the casing of the appliance.

Why will current flow through a person instead of the appliance during a short circuit with a 2-pin plug?

The current flows to earth through the person rather than the appliance which may have a higher resistance.

How does a 3-pin plug provide a precaution against short circuits?

The casing is connected directly to earth, allowing 'leakage' current to flow immediately back to earth.

What simple precaution should be taken for all appliances with metal casings?

They should be properly earthed.

What is recommended regarding the grounding of patients to minimize accidental current exposure?

Where possible, patients should not be grounded (e.g., choice of bed).

Why must large area paddles be used with a defibrillator?

To prevent unwanted burns.

What must be done to both defibrillator electrodes (paddles) before charge and discharge?

They must be isolated from ground.

Can a patient be in contact with ground during defibrillation?

No, the patient must not be in contact with ground.

What restriction applies to physical contact with the patient during defibrillation?

Physical contact with the patient must not occur.

What must be done to monitoring equipment like an ECG during defibrillation?

It must be isolated and current protected.

Where is a fuse connected in an electrical circuit relative to the appliance?

It is connected in series.

What are the physical characteristics of the wire inside a fuse?

It is a thin wire with a low melting point.

How does a fuse break the circuit when current is too high?

The wire melts when current exceeds a pre-determined threshold, breaking the circuit.

What formula is used to calculate the current drawn by a device to select a fuse?

$$P = IV$$

In Ireland, what value of $V$ is used to calculate current for fuse selection?

$$240\,\text{V}$$

How should the fuse rating relate to the current drawn by a device?

The fuse rating should be slightly higher than the current drawn.

What are 'leakage currents' in electrical appliances?

Currents that flow to the case due to a partial breakdown of insulation between the live wire and the case.

What does a Ground Fault Interrupter (GFI) check and compare?

It compares current flowing through the live wire with current returning through the neutral wire.

What does a difference between live and neutral current in a GFI indicate?

A hazardous 'leakage current'.

At what current difference threshold will a GFI 'break' the circuit?

$$\sim 5\,\text{mA}$$

What is the defining characteristic of a microshock hazard?

The current is introduced directly into the heart via an internal electrical path.

By what factor are safety thresholds for current reduced if an internal path to the heart exists?

$$\sim 1000$$

What minimum current level can induce fibrillation in a microshock sensitive patient?

$$20\,\mu\text{A}$$

At a resistance of $1000\,\text{Ohms}$, what voltage can produce a dangerous microshock current?

$20\,\text{mV}$, which is $0.02\,\text{V}$.

List three examples of patients who are considered microshock sensitive.

Patients with pacemakers, inserted catheters, or any internally placed conductor.

What is the second necessary condition for a microshock risk to occur?

The patient must be grounded in some way.

How should microshock sensitive patients be managed regarding ground connection?

They must be completely isolated from ground at all times.

What is the earth requirement for electrical equipment near microshock sensitive patients?

All electrical equipment connected to (or close to) the patient must be individually earthed.

How does moisture in humidified air affect the build-up of static electricity?

It allows excess charge to drain away through attachment to water molecules.

Why is the potential of the earth terminal significant in many appliances?

It is connected to the casing as a safety mechanism.

What happens if a Ground Fault Interrupter (GFI) detects a difference greater than $5\,\text{mA}$?

It will 'break' open the circuit and halt the flow of current.

Why is a 3-pin plug safer than a 2-pin plug during an insulation breakdown?

The 3-pin plug has a connection to earth that diverts leakage current away from the user.

What is the primary role of humidifiers in operating theatres regarding electrical safety?

To maintain humidity to prevent the build-up of static electricity.