91Ó°ÊÓ

Electric current can be compared to the flow of water through a pipe, representing the movement of electric charges (typically electrons) through a conductor. The unit of electric current is the ampere (A), and it is measured by how many charges pass through a given point in a second. In simpler terms, the greater the number of electrons flowing, the higher the current.

In the provided exercise, the wet hands of the fisherman conduct electricity allowing a current to flow through his body when the electric fish generates a potential difference. The value of the electric current, calculated by Ohm's Law as 0.5A or 500mA (milliamperes), indicates a substantial flow of electric charges between his hands.

Electrical resistance is an obstruction to the flow of electric current, similar to friction in mechanical systems. It is measured in ohms (\( \text{Ω} \) ). Factors affecting resistance include the material's properties, temperature, length, and cross-sectional area. Materials with low resistance, such as metals, are good conductors, while those with high resistance are insulators, like rubber.

The exercise shows that the fisherman's wet, salty hands have a low skin resistance of just 100 ohms. This reduced resistance is due to the presence of salt which contains ions, enhancing the conductivity of water. This explains why wet skin is more prone to electric shock than dry skin, as the resistance is significantly decreased, thereby allowing more current to flow.

Potential difference, often referred to as voltage, is a measure of the work done to move a charge between two points in an electric field. The unit for potential difference is the volt (V). It is called a 'difference' because it represents the variance in electric potential energy between two locations.

Within the context of the problem, the torpedo ray creates a 50V potential difference which propels electrons to move through the fisherman's body, thereby generating an electric current. The presence of a potential difference is what causes the electric current to flow; without it, there would be no 'push' to move the electrons. In everyday life, battery terminals have a potential difference between them that causes current to flow when connected in a circuit.