Cardiff Q - Physics Flashcards
‘Ideal gas’ 3 principles
Molecules so far apart there are no attractive forces between them
Volume of molecules themselves are negligible
Molecules are in random motion and obey Newton’s laws of motion
Dalton’s law definition and equation
Total pressure of a gas mixture is the sum of all its individual gas pressures
Pt = P1 + P2 + P3 ….
Boyle’s law
For a fixed amount of gas at a constant temperature, the volume is inversely proportional to its pressure
P proportional 1 / V
Charles’ law
At a constant pressure, volume is directly proportional to temperature
Gay-Lussac’s law
At a constant volume, pressure is directly proportional to its temperature.
Combined gas law
P1 x V1 / T1 = P2 x V2 / T2
Universal gas law
PV = nRT
n = number of moles
R = universal gas constant
Henry’s law
At a constant temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of a gas in equilibrium with it
Vapour definition
Gas below its critical temperature
Latent heat of vapourisation
As vapour molecules picked up by gas flow, resultant vapour liquid cools
Therefore need to maintain temperature as otherwise properties of gas changes (as described in the gas laws)
Mechanism to maintain safe and variable volatile agent use
Bypass channel with splitting ratio modifiable via dial
Desfluorane approximate boiling point
Boiling point very close to room temperature
Ohms law
Voltage = Current x Resistance
V=IR
Approximate resistance of Humans
~ 1500 Ohm
Reduced when wet
What causes damage to tissue from electrocution
Electrical current
Higher current, higher damage
Consideration for severity of shock
Voltage of source
Resistance of body
Timing of shock - eg cardiac rhythm
Electrocution symptoms at 1mA
Tingling sensation
Electrocution symptoms at 5mA
Threshold for “harmless” current
Electrocution symptoms at 10-20 mA
Sustained muscular contraction
‘Can’t let go’ threshold as flexors stronger than extensors in upper limbs
Electrocution symptoms at 100-300 mA
Ventricular fibrillation
Electrocution symptoms at 6A
Respiratory paralysis and burns
Microshocks
Unintended flow of small (but dangerous) currents directly or close proximity to the heart
Bypasses highly resistant skin barrier
Eg central lines, pacing wires
Electrical safety devices / features
Earthing
Isolated systems
Wire insulation
Fuse
Circuit breakers
Residual current device (RCD)
Isolated electrical systems
Uses an isolating transformer to isolate the equipment from the mains power supply
Fuse
Thin wire which melts when certain current reached
Circuit breaker
Similar concept to fuse but uses electromagnets
Classification of electrical equipment
Class 1
Class 2
Class 3
Class 1 electrical equipment
The casing of the equipment must be earthed
Class 2 electrical equipment
Equipment is double insulated so does not require earthing
Class 3 electrical equipment
Separated extra low voltage circuit using isolating transformer
No earthing required
Classification of leakage current based on use of equipment
Type B
Type BF
Type CF
Type B leakage current equipment
Contact with body only
Max leakage current 0.1 mA
Can be class 1,2 or 3
Type BF leakage current equipment
Contact with body only. Isolated from mains (hence F for floating)
Max leak 0.1 mA
Class 3 equipment only
Type CF leakage current equipment
For cardiac equipment
Missed info from this slide so look up the gaps here ……
