At which current level does the risk of severe burns increase significantly?

The correct answer is associated with the understanding of electrical safety and the physiological effects of electrical current on the human body. At a current level of 500 mA (or 0.5 A), the risk of severe burns indeed increases significantly. This level of current can cause a substantial amount of heat generation within tissues, leading to thermal burns.

When electricity passes through the body, it can generate heat due to the resistance encountered by the current. As the current level increases, especially beyond 100 mA, there is a greater likelihood of causing severe damage, not just in terms of potential heart arrhythmias or electrocution but also in terms of burns where the current enters and exits the body.

It's important to note that lower levels, such as 5 mA, 50 mA, and even up to 100 mA, may not typically result in severe burns, although they can still be dangerous. However, once the current reaches 500 mA, the body's tissues begin to experience critical heating, making severe burns a likely outcome if the exposure duration is significant. Thus, the threshold of 500 mA serves as a crucial marker for increased risk of electrical burns.