One device in which capacitors have an important role is the defibrillator (Fig. 26.14).
Up to 360 J is stored in the electric field of a large capacitor in a defibrillator when it is
fully charged. The defibrillator can deliver all this energy to a patient in about 2 ms. (This
is roughly equivalent to 3 000 times the power delivered to a 60-W lightbulb!) Under the
proper conditions, the defibrillator can be used to stop cardiac fibrillation (random contractions)
in heart attack victims. When fibrillation occurs, the heart produces a rapid,
irregular pattern of beats. A fast discharge of energy through the heart can return the
organ to its normal beat pattern. Emergency medical teams use portable defibrillators
that contain batteries capable of charging a capacitor to a high voltage. (The circuitry
actually permits the capacitor to be charged to a much higher voltage than that of the
battery.)