The product of V and I, VI, in an electrical circuit can be understood as the thermal power radiated by the circuit. When current flows through a resistance in a circuit, it causes the electrons to collide with the atoms in the material, generating heat. This heat is represented by the product of the potential difference V and the current I.
Option 1: Resistance R is not the correct answer as it does not represent the product of V and I. Resistance represents the opposition to the flow of electric current in a circuit.
Option 2: Heat generated by the circuit is the correct answer. As explained earlier, when current flows through a resistance, it generates heat due to the collisions between electrons and atoms.
Option 3: Thermal power radiated by the circuit is the correct answer. The heat generated in the circuit can be radiated into the surrounding environment and is represented by the product of V and I.
Option 4: Rate of change of resistance is not relevant to the product of V and I. The resistance of a circuit does not change with respect to the potential difference or current flowing through it.
In conclusion, the correct answer is option 3, which states that the product of V and I represents the thermal power radiated by the circuit.