"A comparison of the dangers of an electric shock from a 240V AC mains supply and various DC voltages from appliances on the body"
You get an Electric shock when a large flow of electricity passages the body. This current depending on the strength will cause an issue and a interruption in the central nervous system of the body which will in most cases produce some effect on the muscles of the body connected to the current, or in more severe cases cause death (often due to heart failure). In the house hold an electric shock will often occur when someone touches a live wire and a connection to the earth.
- The Effect of DC voltages: An electrical shock passed through the human body can cause muscles to contract. This may seem harmless but if the muscles for example used in breathing are involved affects can be disastrous, Often the occupant will be unable to breath this may cause death to the person attached to the live wire.
The effect of AC voltages:
The way an AC current affects the body is largely dependant on the type of frequency. At a low frequency it can actually be more dangerous than if it is the same as DC. AC currents will produce a muscle contraction that makes the human not let go of the live wire where as DC will often force the victim away. AC at high currents can cause the heart to fibrillate which can cause death and why the defibrillator unit is DC, which stops the heart from fibrillation and gives the heart a chance to recover.
Relevant Link: http://science.howstuffworks.com/electric-shock-info.htm