Resistance and Capacitators - check my work.

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SUMMARY

The discussion centers on calculating the resistance needed for a heart pacemaker operating at 71 beats per minute using an 8.5 microfarad capacitor in an RC circuit. The user initially applied the formula R = t / (C * ln[v0 / v]) with t set to 1.183 beats/sec, resulting in an incorrect resistance value of -3.8 x 10^8 ohms. A key error identified is the misunderstanding of the variable 't', which should represent time in seconds rather than beats per second.

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vucollegeguy
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A heart pacemaker is designed to operate at 71 beats/min using a 8.5 microF capacitor in a simple RC circuit.

What value of resistance should be used if the pacemaker is to fire (capacitor discharge) when the voltage reaches 69% of maximum?

Here's what I've done (but my answer was wrong):

R= t / (C*ln[v0 / v])

with t = 1.183 beats/sec
C = 8.5 x 10-6F
v0/v = 0.69

R = -3.8 x 108 ohms

Where did I go wrong?
 
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Hi vucollegeguy! :smile:
vucollegeguy said:
R= t / (C*ln[v0 / v])

with t = 1.183 beats/sec

I'm not an expert on capacitors :redface:

but shouldn't t be a time ? :confused:
 

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