Calculating Energy Delivered by a Pacemaker to the Heart

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Discussion Overview

The discussion revolves around calculating the energy delivered by a pacemaker to the heart, considering various parameters such as resistance, pulse amplitude, pulse duration, and current drain. Participants explore the implications of these parameters on energy calculations, with a focus on theoretical efficiency and practical considerations.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant calculates the energy delivered to the heart using the formula P=V^2/R and finds it to be 7.2x10-6 J, questioning the relevance of the current drain in this calculation.
  • Another participant suggests that the current drain and the stimulation rate may be unnecessary information for the energy calculation.
  • Concerns are raised about the efficiency of the pacemaker, with one participant arguing that if the electronics were 100% efficient, the average current drain would be higher than the stated 2 μA.
  • Some participants discuss the implications of energy conservation and the relationship between power drawn and power delivered, suggesting that the battery voltage could be different from the pulse amplitude.
  • There is a clarification that the current drain is interpreted as the current drawn from the battery, but the actual battery voltage remains uncertain.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of the current drain in the energy calculation, with some suggesting it is not necessary while others believe it raises important questions about the pacemaker's efficiency and battery characteristics. The discussion remains unresolved regarding the implications of current drain on energy calculations.

Contextual Notes

Participants note that the assumptions about efficiency and battery voltage are not explicitly stated in the problem, leading to ambiguity in the interpretation of the current drain and its impact on energy delivery.

Sloan650
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A pacemaker stimulates heart tissue with R of 100ohms.
Pulse amplitude is 1.2 Volts & pulse duration is 0.5ms.
Stimulates at 70bpm
Current drain = 2microamps

Calculate energy delivered to heart from pacemaker at each pulse.

i got

P=V^2/R = 0.0144

Then Energy = Power*time = 0.0144*0.5x10-3 = 7.2x10-6 J

But do i not need to take into account the current drain?
 
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Please help?! its for an exam tomorrow!
 
Sloan650 said:
A pacemaker stimulates heart tissue with R of 100ohms.
Pulse amplitude is 1.2 Volts & pulse duration is 0.5ms.
Stimulates at 70bpm
Current drain = 2microamps

Calculate energy delivered to heart from pacemaker at each pulse.

i got

P=V^2/R = 0.0144

Then Energy = Power*time = 0.0144*0.5x10-3 = 7.2x10-6 J

But do i not need to take into account the current drain?

It would appear that the current drain and the 70bpm figures are superfluous information.
 
Sloan650 said:
A pacemaker stimulates heart tissue with R of 100ohms.
Pulse amplitude is 1.2 Volts & pulse duration is 0.5ms.
Stimulates at 70bpm
If the pacemaker electronics is 100% efficient (unrealistic, but let's consider it to be ideal for sake of argument), then the above information will account for a drain on the battery averaging 7 μA.

Current drain = 2microamps
So I'm puzzled by their figure of just 2 μA. I say it has to be more than 7 μA.

Then Energy = Power*time = 0.0144*0.5x10-3 = 7.2x10-6 J
I agree with this figure, and it has units of Joules.

But do i not need to take into account the current drain?
No. But the person who set the question does need to explain the anomaly. :confused:
 
NascentOxygen said:
If the pacemaker electronics is 100% efficient (unrealistic, but let's consider it to be ideal for sake of argument), then the above information will account for a drain on the battery averaging 7 μA.


So I'm puzzled by their figure of just 2 μA. I say it has to be more than 7 μA.


I agree with this figure, and it has units of Joules.


No. But the person who set the question does need to explain the anomaly. :confused:

The problem doesn't say that the stated current drain is measured at the output of the pacemaker, or that the pacemaker's battery must be 1.2V. For all we know the pacemaker could be running on a 12V battery (okay that's unlikely but you get the idea) and its circuitry is designed to deliver the required pulses via suitable transformation. The concern would be with energy conservation (power drawn >= power delivered), or I*V, rather than just I.
 
The only interpretation of "current drain" is current drawn from the battery. But you are right that the battery need not be 1.2 volts. What it would realistically be, though, I don't know.

Good save.
 

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