AWABS - Capacitors, Inductors and Transformers Flashcards
Capacitor definition
Device which stores electrical charge
Charge definiton
Results due to an excess or deficit of electrons
Unit = Coulomb (C)
Current definition
Flow of electrical charge
Unit = Ampere (I) = Coulomb / second
How capacitors work
2 conducting plates separated by a dielectric (dielectric is an insulator not a conductor)
Becomes charged when a potential difference is applied across it
Measure of charge stored (capacitance)
Farads (F)
1 farad = 1 C of charge stored if a potential difference of 1 V is applied to it
DC current
Direct current
AC current
Alternating current
Inductors definition
Device which opposes the flow of current by generating an electromotive force
Inductor electronic symbol and appearance in real life
Inductor features
Unit = Henry (H)
Transformer definition and symbol
How do transformers work
Defibrillator definition
A device used to restore normal cardiac rhythm by delivering a controlled electrical charge
Defibrillator circuit and how it works
Defibrillator charging vs discharging circuit
Role of inductor in defibrillator discharging circuit - graph included
Lower peak current to reduce risk of burns and
Prolongs duration of discharge to increase chance of successful defibrillation / return to normal cardiac rhythm
Features of biphasic defibrillators
Only use biphasic defibrillators now
Thoracic impedance definition
Opposition to current flow across chest
Changes throughout cardiac cycle
Higher impedance means higher current required to achieve same energy
Calculating energy delivered by defibrillator
E = 1/2 CV^2
ICD acronym
Implantable cardioverter defibrillator
ICD vs pacemaker on CXR
ICD has thicker wires
