An iron ball at 50°C is dropped in a mug containing water at 50°C. Which of the following observation is true?

The heat will not flow from iron ball to water or from water to iron ball.

The correct answer is option 2. The heat will not flow from iron ball to water or from water to iron ball.

When two objects at the same temperature come into contact, there is no net heat flow between them. This is based on the principle that heat naturally flows from a higher temperature to a lower temperature until thermal equilibrium is reached.

In the scenario described:

1. The iron ball and water are both at 50°C.

2. Since they are at the same temperature, there is no temperature difference to drive the heat transfer.

3. Heat transfer occurs when there is a temperature gradient (difference), and in this case, that gradient is zero.

4. As a result, there is no net heat flow from the iron ball to the water or from the water to the iron ball.

Therefore, the temperatures of both the iron ball and the water will remain constant, and there will be no change in their thermal energy.