Primary FRCA Course Electrical Safety Exam Prep Questions Flashcards
In micro shock:
The current is too small to be harmful
False. Even small currents applied directly to the heart produce a current density sufficient to have a biological effect
In micro shock:
The frequency of the current is not important
False. The effect of frequency in microshock is the same as in macroshock. Higher frequency means that charge is moved less far as oscillations are more frequent. So in the case of the body, the ions are moved less far, therefore less likely to cross the cardiac membrane and cause VF.
In micro shock:
The right ventricle is more sensitive than the left
True.
In micro shock:
The current must be greater than 100uA
False. Currents of over 50uA are sufficient to have an effect
In micro shock:
The current may induce asystole
False. Typically cause VF especially if delivered during repolarisation.
In electric shock:
Frequencies of >10KHz do not cause arrhythmias
False. It depends to some extent on the size of the current, but the frequency should be >100KHz
In electric shock:
Effect depends upon the duration of current flow
True. Both energy delivery and ion shifts depend upon ‘quantity’ of charge passed (current and time)
In electric shock:
Current mainly affects the flexor muscles
False. But your forearm flexors are stronger than your extensors, hence the inability to ‘let go’
In electric shock:
Effect depends on the total amount of energy delivered
True. Both energy delivery and ion shifts depend upon ‘quantity’ of charge passed (current and time)
In electric shock:
Electrons flow through the body
False. The charge carriers in the body are ions
The electricity supply to an operating theatre:
Is a three phase supply
False. Only a single phase is supplied to the operating room. Three phase is supplied to hospital substation.
The electricity supply to an operating theatre:
Consists of Live, Neutral and Earth wires
False. LINE neutral and earth wires
The electricity supply to an operating theatre:
Has a voltage of approximately 240 volts
True.
The electricity supply to an operating theatre:
Has an Earth connection from the substation
False. The substation earth (star point) creates the ‘Neutral’ wire. The earth connection is a local earth
The electricity supply to an operating theatre:
Varies sinusoidally at 50 Hz
True. Mains frequency is held very close to 50 Hz in europe (60 Hz in the USA)
Electrostatic interference from a piece of equipment:
Requires a current to flow in the power wires
False. For electrostatic interference NO CURRENT is required in either wire.
Electrostatic interference from a piece of equipment:
Is easily prevented by using screened cable
True. Electrostatic fields will not pass through a conductive barrier
Electrostatic interference from a piece of equipment:
Is reduced by insulating the signal leads
False. Insulation will not prevent an electrostatic field affecting the wires inside the insulation. The wires must be encased in a conductive NOT insulating layer
Electrostatic interference from a piece of equipment:
Is minimised at high frequencies
False. Would be increased at high frequency. Electrostatic interference is a form of capacitive linkage
Electrostatic interference from a piece of equipment:
Is halved by doubling the separation between signal and power leads
True. Doubling the separation, halves the field strength between the two wires.
Electromagnetic interference:
Requires the source of the interference to be drawing (using) current
True. When an alternating current is flowing an alternating magnetic field is generated around the power wire and this induces current in the signal lead.
Electromagnetic interference:
With an ECG monitor can be prevented by using screened leads
False. Screening does NOT prevent the magnetic field from affecting the signal wires.
Electromagnetic interference:
Is halved by doubling the separation between signal and power leads
False. Magnetic field strength varies as the reciprocal of the separation SQUARED.
Electromagnetic interference:
Does not affect battery powered equipment
False. Battery powered equipment is just as likely as mains powered equipment to be affected by an external magnetic field