Time Constant, Resistance, Energy

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Homework Help Overview

The problem involves a capacitor in a heart defibrillator unit, specifically focusing on the time constant, resistance, and energy delivered through an RC circuit. The capacitor is charged to a high voltage and connected to a patient's chest, with various questions regarding the time constant, resistance, and energy loss over time.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the time constant and resistance in relation to the given capacitor specifications. There are attempts to clarify the capacitance value and its role in the equations provided. Some participants express uncertainty about the correct equations to use for the calculations.

Discussion Status

The discussion is ongoing, with some participants seeking clarification on capacitance and others attempting to address the initial questions. There is a recognition of the given capacitance value, but confusion remains regarding its application in the context of the problem.

Contextual Notes

Participants are working within the constraints of the problem statement and the provided equations, with some expressing uncertainty about their understanding of the concepts involved.

matt72lsu
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Homework Statement



A 11.0 uF capacitor in a heart defibrillator unit is charged fully by a 12000 V power supply. Each capacitor plate is connected to the chest of a patient by wires and flat "paddles," one on either side of the heart. The energy stored in the capacitor is delivered through an RC circuit, where R is the resistance of the body between the two paddles. Data indicate that it takes 72.1 ms for the voltage to drop to 20.0 V.

a) time constant?
b) Determine resistance "R"
c) How much time does it take for the capacitor to lose 89% of its stored energy?
d) If the paddles are left in place for many time constants, how much energy is delivered to the chest/heart area of the patient?

Homework Equations



T = RC (im not sure how to find capacitance)
q = qoe^-t/RC ?

The Attempt at a Solution


i attempted a nd b and got them wrong. for c and d i really have no clue how to start. I am pretty sure I am using the wrong equations. Any help would be appreciated
 
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can someone help me figure out capacitance?
 
Last edited:
anybody?
 
matt72lsu said:
can someone help me figure out capacitance?

The capacitance is 11.0 uF (micro-farads). It's given right in the beginning of the problem.
 

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