The alternating current has a frequency of 50 Hz in India whereas it is 60 Hz in U.S. The alternating current flows to and fro in phase and neutral of the line whereas the direct current flows from positive terminal to negative terminal of the supply hence the frequency of DC is 0 Hz.
- The human body has a nervous system which plays a vital role in the coordination of muscles.
- The central nervous system is connected to various muscle groups and to the brain.
- The nervous system carries tiny electrical signals of magnitude of few micro amps from brain to the muscles.
- The brain sends command to the nervous system which carries small electrical pulses to the muscles which contract and relax.
- The periodic cycle of these electrical signals is 12 to 16 cycles per minute which causes the heart to pump the blood.
- The heart muscle requires a sufficient amount of time to contract and relax to pump the blood from heart to various parts of body.
- If at all the electric current flows through the body which has higher magnitude, the body cannot handle such contractions and relaxations of muscle due to which the muscle gets contracted and attains a freeze mode.
There is no time to relax the muscle thus the person gets attached to the live conductor. Since the heart and lungs doesn’t give sufficient amount of time to relax,the blood circulation and the breathing is stopped. This entire phenomenon is known as fibrillation.
In case of direct current, the person will not experience a shock at smaller voltages whereas the person might get shock at higher voltages because there is no frequency change and the effect on heart is only at once.
If the victim is suffering from a shock and he is still attached to line then he must be disconnected from the supply line using a wooden stick. A heart massage followed by artificial breathing is necessary in order to save the victim from death.
Thus, it is important to know about the phenomenon of shock and how to relieve a person from it. We must be aware about not to touch any bare wire.
- Electrical power systems by Sunil. S. Rao
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