Wheatstone bridge and strain gauges
The typical Wheatstone bridge arrangement as shown above contains a power source, a galvanometer (G), two resistors of known resistance (R1, R2), a variable resistor (R4) and an unknown resistance,…
ANESTHESIA
Gas analysis
Photo-acoustic spectrometry has a higher accuracy, better reliability and does not need as frequent calibration compared to infrared absorption spectrometry. What are the common causes of error with infrared analysers?…
Light and optical fibres
html xmlns=”http://www.w3.org/1999/xhtml” xmlns:mml=”http://www.w3.org/1998/Math/MathML” xmlns:epub=”http://www.idpf.org/2007/ops”> Chapter 29 Light and optical fibres Basic science Light is the part of the electromagnetic spectrum that is visible to the human eye. It has wavelengths…
Electricity – generation and distribution
Three-phase power leaves the power station via three wires (one for each phase of AC) to enter a step-up substation. Here, transformers convert the power station output to a very…
Resonance and damping
Damping results in oscillations of reducing amplitude due to the loss of energy to the surroundings. It is measured as the damping coefficient, which refers to the amount of damping…
EEG and EMG
Applied science How are the EEG and EMG used in anaesthesia? Performing a complete EEG with 20–22 electrodes in the intraoperative environment is not practical and the raw EEG is…
Physics of gases
where P is absolute pressure (Pa), V is volume (m3), n is amount of substance (mol), R is the universal gas constant (8.314 J·K−1·mol−1), and T is temperature (K). Boyle’s…
Fluid dynamics: laminar and turbulent flow
where Q is flow, ΔP is pressure gradient, r is radius, η is fluid viscosity and l is length. From this equation, it can be seen that flow is directly…
Medical gases: storage and supply
Applied science How do you determine how much gas remains in a cylinder? For cylinders containing compressed (non-liquefied) gas, gauge pressure falls as gas is used; Boyle’s law can be…
