Physics MCQ 6 Flashcards
Define critical temperature
Temperature above which a gas cannot be liquified
What is oxygens critical temperature and boiling point?
Critical temp: -118 degrees C
Boiling point: - 183 degrees C
Color of oxygen cylinder
Black body with white shoulders
Color of air cylinder
Grey body with white and black shoulders
How many atoms oxygen molecules form in
O2 and O3
What is absolute humidity?
Mass of water vapour present in a volume of air
What is the characteristic property of dew point?
Full saturation- 100% humidity
What do wet and dry hygrometers calculate?
Relative humidity
How does temperature affect the amount of water vapour present?
Amount of water vapour present in air is dependent on its VAPOUR PRESSURE.
Vapour pressure is proportional to temperature so warm air holds more water vapour.
What is the relative humidity of the trachea?
100% saturated
MRI: T/F
- Contain two electromagnets aligned perpendicularly
- Images are generated by amplifying signals produced by the precession of hydrogen atoms.
- Magnetic flux density of?
- Relies on absorption and reabsorbtion of energy from radio frequency waves
- Liquid helium is used in magnets to reduce resistance in the electromagnet
- True
- True
- Up to 1 Tesla
- True
- True
Is p<0.05 more significant than p<0.01?
No, p< 0.05 means that after the statistical test there is less than 5% chance if the null hypothesis being rejected by chance.
Therefore p< 0.01 (less than 1% chance) is more significant than p < 0.05.
In positively skewed data is the median greater than the mean?
Positively skewed data is skewed to the right, so the mean tends to lie to the right of the median value
- is the lower of the two.
What percentage of the population lies within two standard deviations of the mean?
95%
The standard error of the mean is:
- the square root of the variance
- is the standard deviation divided by the square root of the degrees of freedom (the number of observations - 1)
What does the non-interchangeability of the probes depend upon?
The different sizes of the collars on the probe.
What is the driving pressure of pneumatically driven ventilators?
400kPa, 4 bar (ie standard pipeline pressure)
What are “bag in bottle” ventilators?
A pneumatically driven ventilator
- in “bag in the bottle” ventilators driving gas is separated from fresh gas pneumatically.
What is the failsafe device in the event of gas failure in a pneumatically driven ventilator?
None, if the gas stops working the ventilator stops.
What is the bandwidth used in ECGs?
0.05 - 100 Hz
What size potentials are measured by ECG?
Is a step down transformer required?
Small potentials, in the order of millivolts therefore a step down transformer is not required.
What is the gain of an amplifier?
What units is it measured in?
The gain is the ratio of the amplifier output to the signal voltage.
Measured in decibels.
What does the SD represent?
It is a measure of the spread around the mean in a scatter of observations with a normal distribution.
Only calculated if there is a normal distribution.
How is SD calculated and does it indicate the significance of the observations?
- it is the square root of the variance of the observations
- it says nothing about their significance.
What data does the Chi squared test apply to?
It is a test for non-normally distributed data.
What are anaesthetic gas cylinders made of?
Molybdenum steel alloy
What form is nitrous oxide stored at room temperature?
Liquid
In anaesthetic gas cylinders what is the filling ratio?
The filling ratio is the MASS of contents divided by the MASS of water the cylinder could hold
What is the filling ratio for nitrous oxide cylinders in the UK?
No more than 0.7
Anaesthetic gas cylinders may cool if gas flow rates are high. True or false?
TRUE -»_space; Boyles Law,
If pressure in the cylinder is rapidly reduced by high flow rates, it’s temperature will fall.
Rapid flow results in rapid vaporisation in nitrous oxide cylinders, hence loss of heat from the contents.
Oxygen percentage at higher altitude is lower?
No, the percentage stays the same as at sea level but the partial pressure is reduced.
What is the relative humidity of air in the trachea?
By the time air is in the trachea it is usually 100% saturated.
What are wet and dry hygrometers used to calculate?
Relative humidity
MRI uses two magnets aligned perpendicularly? T/F
True
What flux density does MRI use?
Up to 1 Tesla
In positively skewed data, which is greater, mean or median?
in positively skewed data, the mean is greater than the median.
What is the driving pressure required for a pneumatically driven ventilator?
400 kPa or 4 bar, i.e. standard pipeline pressure.
What is an exponential process?
An exponential process is one in which the rate of change of a substance is proportional to the amount of substance present.
Which of these are exponential processes?
A. filling a bath from a tap connected to mains water supply
B. emptying a bath
C. the height of an adult plotted against age
D. the washout of a gas from the lungs
E. a graph of the volume of a gas plotted against pressure
A. False. The mains water supply should be at a more or less constant pressure so filling a bath will be directly proportional to the pressure.
B. True - emptying the bath is a negative exponential process, i.e. it gets slower the less water is left in the bath.
C. False. The height of an adult is approximately constant until old age when there is often a non-exponential decline
D. True
E. False. Volume varies inversely with pressure (Boyle’s Law) and the graph has a rectangular hyperbola shape
