Approximately what current level is dangerous and can stop a person's heart?

• A. 10-20 mA
• B. 50-100 mA
• C. 500 mA
• D. 100-200 mA

Answer: (D)

Current through the heart is the factor that determines danger. At typical power frequencies (about 60 Hz AC), a current around 100 mA flowing through the chest can disrupt the heart’s normal rhythm and cause ventricular fibrillation, effectively stopping the heart’s coordinated pumping. This is why a range around 100–200 mA is regarded as capable of stopping the heart, though the exact outcome depends on how long the current lasts and the path it takes through the body. Lower currents, such as 10–20 mA, are usually just felt as a tingling or shock without stopping the heart, while 50–100 mA can produce strong muscle contractions and breathing difficulty but is less likely to cause immediate heart stoppage. Much higher currents, like around 500 mA, are extremely dangerous and can cause severe burns and fatal outcomes as well. So, the threshold where heart rhythm disruption becomes a real risk sits in the 100–200 mA range.