If the heat source were turned off, what would happen to the temperature of the rod?

If the heat source were turned off, the temperature of the rod would gradually decrease. Here's a step-by-step explanation:

1. Initially, when the heat source is on, it provides a constant supply of heat energy to the rod. This energy is absorbed by the rod, causing its particles to vibrate more rapidly and thus increasing its temperature.

2. When the heat source is turned off, it stops supplying heat energy to the rod. However, the rod's particles are still vibrating from the previous heat energy they absorbed.

3. Over time, the rod's particles will start to lose their energy. This is because they are constantly colliding with each other and with the surrounding air particles, and each collision causes them to lose a little bit of their energy.

4. As the rod's particles lose energy, they start to vibrate less rapidly. This means that the temperature of the rod decreases.

5. Eventually, if left long enough without a heat source, the rod's temperature will drop down to match the temperature of its surroundings. This is a process known as thermal equilibrium.