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# The Electrical Resistance of the Heart watch

1. Ok so in my lecture notes we are given an example calculating the resistance of the heart and i will literally copy down exactly what's in my notes onto here. I missed that lecture, so i'm a bit confused. for starters, the equation doesn't even equal 25

Consider the heart in the centre of the thorax

thorax: phi=30cm (not sure what the symbol phi is)
resistivity = 2ohm m

heart: phi=50mm
length=100mm
resistivity=20ohm m
potential diff = 5mV

R = resistivity x L / a =(2 x 100 x 10^-3)/(pi x 0.625 x 10^-3) = 25ohms

they've used resistivity of the thorax, not the heart then where does 0.625 come from? it's obv in mm

thanks!!

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