Electricity
What are the deflections seen on an electrocardiogram trace due to?
Pressure differences created by ventricular contraction
The closing and opening of heart valves
The de- and repolarisation of the cells of the myocardium
Variation in the electrical properties of oxygenated blood and deoxygenated blood as it moves through the heart
The de- and repolarisation of the cells of the myocardium
The P wave is due to the depolarisation of the atria, the QRS due to the depolarisation of the ventricles and the T due to the repolarisation of the ventricles.
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Choose the alternative which correctly completes the following sentence: “There are two types of electric charge called:A. Protons and electrons and they attract each other”.
B. Positive and negative and they attract each other”.
C. Anions and cations and they repel each other”.
D. Electrons and ions and they repel each other”.
Why does a correctly installed earth wire provide protection against electrocution by a faulty electrical device? Because:
A. It is made of thick copper wire so presents almost zero resistance.
B. A fuse is located on the earth wire which will “blow” if excessive current flows.
C. The earth wire is connected to the ground and to the metal case of the appliance.
D. The on/off switch is on the earth wire so that power can be turned off.
For patients in a medical treatment room that are receiving an intravenous infusion driven by an electrical pump, what term is used to describe the electrical supply to the room?
A. Cardiac-protected
B. Body-protected
C. Equipotentially earthed
D. Double insulated
In an Australian domestic AC electrical circuit, what is the potential difference (voltage) in the three wires?
A. Active wire oscillates between +240 V and โ240 V, while neutral and earth are both at 0 V.
B. Neutral wire at โ240 V, active at +240 V, earth at 0 V.
C. Active wire at +240 V, while neutral and earth are both at 0 V.
D. Neutral wire and active wire both at +240 V, earth at โ240 V.
The potential differences generated by the heart muscle as it contracts and relaxes can be measured by placing electrodes on the surface of the body. What is the record of these electrical events correctly called?
A. An electrocardiogram
B. Limb lead II
C. An electrocardiograph
D. An EEG
In an electrical device, a correctly installed earth wire provides protection against what?
A. The electrical device receiving too high a current.
B. It protects the fuse or circuit breaker from too much current.
C. Electrocution of a person touching the faulty electrical device.
D. It protects against stray currents that may exist in the ground (the soil).
Inside a typical household is electrical appliance that has a three prong plug, what is the earth wire connected to?
A. The fuse
B. The neutral wire
C. The metal casing
D. The on/off switch
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