Lightning, Electrocution, and Autopsies

[Roman Soldier]

A woman electrocuted her husband in the bathtub and tried to make it look like a lightning strike had killed him on an episode of my favorite show. The deputy said he was going to order a full autopsy, and that they would know if it was lightning or electrocution.

How could they tell?

 

[Skeptical]

[size=-1]A typical lightning strike produces 10 - 100 million volts and 1- 300 thousand amps. An appliance plugged into a 120 V electric socket may produce a current on the order of milliamps within a bath tub filled with tap water.

Electocution occurs when [/size]0.006-0.2 amps (that's 6-200 milliamps) of current flowing through the heart disrupts the normal coordination of heart muscles. This takes on the order of 1 - 3 seconds.

Obviously, both lightning and an electic appliance are capable of causing electrocution but for different reasons. Lightning strikes typically occur at 1/1000 to 1/10 of a second but generate tremendous amperages that can stop the heart muscle instantaneously. Electified bath water causes electrocution because of the prolonged exposure to the milliamperage current flowing through the water, skin, tissue, and eventually, the heart.

The physical effects are different as well. Lightning is a direct current which flows expeditiously from the body to a single ground while a plugged appliance generates an alternating current in which the current direction changes at a frequency of 60 cycles per second (Hertz). An alternating current will generate a spasmodic contraction and release of most muscles which will be borne out in tissue damage as well as elevated levels of lactic acid in the body during the autopsy.

 

[Darkhorse]

From what I've studied in criminal investigation, lightning often produces a large distinctive "arboreal" or tree-shaped burn on the body, usually on the chest. Also, high voltage (and thus high amperage) often produces burns in internal organs, which can probably be detected by autopsy.

 

[Quantos]

From what I've studied in criminal investigation, lightning often produces a large distinctive "arboreal" or tree-shaped burn on the body, usually on the chest. Also, high voltage (and thus high amperage) often produces burns in internal organs, which can probably be detected by autopsy.

one minor correction

High Voltage dose not mean High Amperage
I=E/R the larger the Resistance for a Given Voltage the lower the current.

Look at static electricity (Like the shock you get when you touch a doorknob), it's in the 100,000V range if I'm correct. but the current is very small.

But a Car battery (12V) can supply enough current to cook you.

 

[Darkhorse]

I agree that a high voltage does not ALWAYS produce a high amperage (as with your static-electricity and car battery examples), but where a great deal of energy is available (lightning or powerline) a higher voltage will produce a higher current flow (amperage). Look at your Ohm's Law: if R remains constant and E increases, "I" will also increase.

Good talking to you...

 

[DaveS]

umm.. I'm guessing that 'R' is resistance, 'E' is voltage and 'I' is current?

Over here we have V = IR with 'V' being voltage, 'I' being current and 'R' being resistance.

Strange huh?

 

[ImmortalAwakened]

A woman electrocuted her husband in the bathtub and tried to make it look like a lightning strike had killed him on an episode of my favorite show. The deputy said he was going to order a full autopsy, and that they would know if it was lightning or electrocution.

How could they tell?

Voltage maybe. Lightning strikes may be stronger than water electrocutions.

 

[Quantos]

umm.. I'm guessing that 'R' is resistance, 'E' is voltage and 'I' is current?

Over here we have V = IR with 'V' being voltage, 'I' being current and 'R' being resistance.

Strange huh?

Not really

I=E/R
E=I*R
R=E/I

are all the same, just solving for I,(E or V) or R

 

[DaveS]

Not really

I=E/R
E=I*R
R=E/I

are all the same, just solving for I,(E or V) or R

Yeah I know, I was just saying it was strange about E or V..