Final answer:
A shock causing burns and muscle contractions is related to the effects of electric current on the body, with higher currents posing increased risks of ventricular fibrillation and burns.
Step-by-step explanation:
A shock that passes through a small part of the body, causing burns and muscle contractions, is known to have varied effects depending on the intensity of the electric current. At a current level of about 300 mA and above, there is a greater likelihood of burns, especially if the current is more concentrated. Furthermore, currents in this range can stimulate involuntary muscle contractions and may also result in ventricular fibrillation—a condition where the heart beats irregularly and ineffectively, which can be fatal.
Ventricular fibrillation often persists after the shock has ended and is a critical concern because it disrupts blood circulation. At currents between 5-30 mA, muscle contractions can be stimulated, similarly to natural nerve impulses. At higher currents, the electrical shock could even 'throw' a person backward due to the forceful extension of muscles, and in some cases, victims may not be able to release their grip on an electrified object.