AC or DC
All things being equal, which is more harmful to the human
body. AC or DC? ALL THINGS BEING EQUAL. (length of exposure, amps,
voltage, area involved, etc...) The important thing here is which one is
the most damaging (causes more harm)or is more fatal.
It depends on the frequency of the AC. All AC is not equal. It's also hard
to directly answer your question, because we can't experiment with
electrocuting human subjects. The "let-go" current is the best experimental
measure we have of the effect of electricity on humans. The "let-go"
current is the lowest level of current passing through a human subject
through an electrode held in the hand that makes the subject unable to open
his hand and drop the electrode. (From what I understand, the experiment
hurts, but it isn't permanently damaging to the subject.)
It turns out that the "let-go" current starts at some finite value at a
frequency of zero (DC), passes through a minimum, and then increases as the
frequency gets higher. (At high frequencies, the only known harm from AC is
the resistive heating of the subject's tissues.) This means, that, using
"let-go" current as the measure of hazard, there is a frequency of AC that
is more dangerous than others. Ironically, this most dangerous frequency is
around 60 Hertz, which is the frequency of the AC supplied by electric
utilities in the US.
Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
This is a very general question since it does not discern between the
possible harmful secondary effects of the electrical source EMF and is not
clear whether it is referring just to electrocution. I will briefly respond
to just the electric shock difference between the two.
The amount and kind of injury depends on six things - voltage, amperage,
resistance, type of current, path of current, and duration of exposure.
Voltage is a measure of electrical force. The greater the voltage, the
greater the tissue damage. Voltage typically ranges from a house current of
120 volts to a high-tension wire current of 1,000 volts or more.
Type of current means whether the charge is AC or DC. Lightning is a direct
current (DC) which possesses much stronger voltage than a high-tension wire.
Generated electricity packs far less power and is an alternating current
In humans, since AC is an alternating current, if a person is shocked by AC
they will be seen to be shaking in sympathy with the frequency of the
alternating current. If the current passes through the heart, by a person
holding a live wire in their left hand and their right foot is in water and
not their left, then there is a much greater chance the current will effect
the pacemaker of the heart and possibly cause fibrillation (where the heart
pumps little to no blood). DC current, tends to jolt the person with no
shaking but still can have the same effect in that if the current runs
through the heart it can have serious consequences. In both these
situations the amount of current is of course very important.
Amperage is the flow of the current and, when combined with voltage, is what
causes the most damage. The greater the amperage, the greater the damage to
Click here to return to the General Topics Archives
Update: June 2012