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.
