Portable cardiac defibrillators often rely on a capacitor that can deliver a sudden…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Portable cardiac defibrillators often rely on a capacitor that can deliver a sudden burst of electrical energy. A particular model uses a capacitor with capacitance C=120μF and must store 360J of energy just before discharge.
(a) Determine the potential difference that must exist across the capacitor plates to store the required energy.
(b) Suppose an engineer wishes to build this capacitor as a parallel-plate device using two square aluminum plates of area 100cm2 each, separated by a plastic dielectric whose constant is κ=3.4. Calculate the plate separation that would achieve the desired capacitance.
(c) Evaluate whether a plate separation of less than 1.0mm is achieved. Discuss briefly one practical advantage or drawback of your result for the design of the defibrillator.