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MCAT

Unit 3: Lesson 1

Chemical and physical sciences practice passage questions

Cardiac dysrhythmia and defibrillators

Problem

Cardiac dysrhythmia, or irregular heartbeat, is a condition that can have a number of causes and manifestations. One example of this is fibrillation, a condition in which the heart erratically contracting due to spontaneous electrical impulses from the cardiac nodes.
A defibrillator is a device that charges up and can deliver a large amount of electrical energy in a short amount of time to someone suffering from cardiac dysrhythmia. This burst of electrical energy has the potential to briefly stop a heart that is beating irregularly. The heart will then immediately restart, and will often revert to a steady, normal beating pace again, as the spontaneous impulses have now been eliminated. One of the main components in a defibrillator is a capacitor.
Figure 1. Defibrillator placement on a patient with cardiac dysrhythmia.
The hospital you work for uses a defibrillator that has a single capacitor with a capacitance of 10start superscript, minus, end superscriptstart superscript, 6, end superscript F. When it is about to be used, the defibrillator is charged to a voltage of 4000 V.
How much charge is stored on the defibrillator ‘s capacitor when it has been fully charged?
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