Ac is more dangerous than d.c, a.c is said to be four to five times more dangerous than d.c for one thing a.c cause more severe muscle contractions for another. it stimulates sweating, which lowers the skin resistance.
- The type of current affects the severity of the injury in general,direct current (DC) which has zero frequency but maybe intermittent or pulsating. is less dangerous than alternating current (AC)
- Dc tends to cause a convulsive contraction, often forcing the victim away from the current source. Ac at 60Hz (household current) produces muscle tetarity, often freezing the hand to the current sources prolonged exposure may result with severe burns if the voltage is high.
- the effort of ac on the body depend largely on the frequency. low frequency currents of 50 to 60Hz which are commonly used are usually more dangerous than high frequency currents are 3 to 5 times more dangerous than Dc of the same voltage and amperage.
- Dc is less dangerous
- Ac is more dangerous
- high frequency current
- low frequency current penetrates
Facts about Electric Shock
- It is the magnitude of current and the time duration that produces effect. That means a low value current for a long duration can also be fatal. The safe current/time limit for a victim to survive at 500mA is 0.2 seconds and at 50 mA is 2 seconds.
- The voltage of the electric supply is only important as it ascertains the magnitude of the current. As Voltage = Current x Resistance, the bodily resistance is an important factor. Sweaty or wet persons have a lower body resistance and so they can be fatally electrocuted at lower voltages.
- Let-go current is the highest current at which subject can release a conductor. Above this limit, involuntary clasping of the conductor is present. It is 22 mA in AC and 88 mA in DC.
- Placing your hand in your pocket may protect you by preventing a current from traveling through the heart making a shock non-lethal.
- The severity of the electric shock depends on the following factors: body resistance, circuit voltage, amplitude of current, path of the current, area of contact, and duration of contact.
- Low frequency AC is more dangerous than high frequency AC.
- AC and DC both kill so treat them with respect
Effects of an AC or DC Currents on the Human Body
The three basic factors that determine what kind of shock you experience are the amplitude of the current, the duration of the current passing through the body, and the frequency. direct currents actually have zero frequency, as the current is constant. However, there are physiological effects during electrocution no matter what type of current.
The factor deciding the effects of the AC and DC current is the path the current takes through the body. If it is from the hand to the foot, it does not pass through the heart, and then the effects are not so lethal.However DC current will make a single continuous contraction of the muscles compared to AC current, which will make a series of contractions depending on the frequency it is supplied at. In terms of fatalities, both kill but more milliamps are required of DC current than AC current at the same voltage.
If the current takes the path from hand to hand thus passing through the heart it can result in fibrillation of the heart. Fibrillation is a condition when all the heart muscles start moving independently in a disorganized manner rather than in a state of coordination. It affects the ability of the heart to pump blood, resulting in brain damage and eventual cardiac arrest.Either AC or DC currents can cause fibrillation of the heart at high enough levels. This typically takes place at 30 mA of AC (rms, 60 Hz) or 300 – 500 mA of DC.