Conduction is possible

Options

A. when the bodies are far apart from each other.
B. when the bodies have same temperature and in thermal contact.
C. when they have different temperatures maintaining distance between them.
D. when the bodies are in contact and have different temperatures.

Answer

### Step-by-Step Solution:

1. **Understanding Conduction**:
- Conduction is a mode of heat transfer that occurs within a body or between two bodies that are in direct contact. It involves the transfer of thermal energy from the hotter part of the body to the cooler part.

2. **Conditions for Conduction**:
- For conduction to occur, two main conditions must be satisfied:
- **Contact**: The two bodies must be in physical contact with each other. This means they should touch; heat cannot transfer through air or any other medium without contact.
- **Temperature Difference**: There must be a temperature difference between the two bodies. Heat will flow from the hotter body to the cooler one until thermal equilibrium is reached.

3. **Example of Conduction**:
- Consider two rods: one cold (e.g., at 20 degrees Celsius) and one warm (e.g., at 70 degrees Celsius).
- When these two rods are touched together, heat will transfer from the warm rod to the cold rod because of the temperature difference.

4. **No Heat Transfer Without Temperature Difference**:
- If both rods are at the same temperature (e.g., both at 50 degrees Celsius), there will be no heat transfer. This is because there is no temperature gradient to drive the conduction process.

5. **Conclusion**:
- Therefore, conduction is possible when two bodies are in contact and have different temperatures. The correct answer to the question is that conduction occurs under these conditions.