Effect of current

Hi all
In my text book is says : contact with voltage as low as 32v ac or 115v dc can lead to asphyxia , ventricular fibrillation etc
My question is why does it matter if it is ac-dc ? If 32v ac can hurt wouldn't 32v dc do the same damage ?

Just started studying so sorry for the stupid question
Thanks

Via iPhone

It has been shown that to cause fibrillation which leads to cardiac arrest, that it takes less AC current to do so than DC current. "60 mA of AC (rms, 60 Hz) or 300–500 mA of DC can cause fibrillation":http://en.wikipedia.org/wiki/Electric_shock

Is that because alternating current is causing more damage on the heart ?

Yes...It sounds like it causes more tissue damage.

I don't think it is damage, I think it is that it causes fibrillation because it is reversing 50 or 60 times a second.

A DC current can cause the muscle to lock up, and the heart may restart after the current is removed.

When a doctor tries to restart your heart, they use a big pulse of current in one direction, not AC. The idea is to cause the non-coordinated fibrillating heart muscle cells to all lock up for a moment, then naturally restart together.

That Wikipedia page agrees with my testing, in that most of your body's resistance is in the skin and the internal tissues can be around 500 ohms, depending on where and how deeply you puncture. At 5V, that is 10mA, which as the Wikipedia page points out can be lethal if the current is directed across the heart.

Fortunately it is highly unlikely that you'll somehow puncture one hand on your computer's 5V or 12V buss while simultaneously puncturing the other hand or opposite foot on a ground.

Haha
Thanks guys for ur answers
Richard

When you say 32v ac it means RMS value . So the peak value would be 1.414 tmes of rms voltage , well that shoots up the voltage !! So 32v Dc is not same as 32v Ac.

Good point, but 32Vrms x 1.4 ~ 45Vpk, hardly 115Vdc.

It is the current that determines damage. Voltage is required to push the current.

True! Current determines the damage so will be the voltage! Current and voltage are two Different things , we may argue Voltage is directly proportional to current (Ohms law) .
The 10v Dc may be Small to cause a current in the body , but the 5amps(say) it is producing is enough to give the body a shock!!

Thanks for sharing!