In a metal with positive Thomson coefficient, current is passed from the lower temperature to higher temperature side. Then heat will be

Options

A. absorbed
B. constant
C. evolved
D. either 'b' or 'c'

Explanation

To solve the problem regarding the heat flow in a metal with a positive Thomson coefficient when current is passed from the lower temperature to the higher temperature side, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Thomson Effect**: The Thomson effect describes the heating or cooling of a conductor when an electric current passes through it and there is a temperature gradient. The Thomson coefficient (denoted as \( \mu \)) indicates the amount of heat produced per unit charge that flows through the conductor per degree of temperature difference.

2. **Given Information**:
- The Thomson coefficient is positive.
- Current is flowing from the lower temperature side to the higher temperature side.

3. **Direction of Heat Flow**:
- In a metal with a positive Thomson coefficient, when the current flows from the lower temperature side to the higher temperature side, heat is absorbed from the lower temperature side and released at the higher temperature side.

4. **Heat Generation**:
- According to the Thomson effect, the heat generated (or absorbed) can be calculated using the formula:
\[ Q = \mu \cdot I \cdot \Delta T \]
- Where:
- \( Q \) is the heat generated,
- \( \mu \) is the Thomson coefficient,
- \( I \) is the current,
- \( \Delta T \) is the temperature difference.

5. **Conclusion**:
- Since the Thomson coefficient is positive and the current flows from the lower temperature to the higher temperature side, heat will be absorbed by the conductor from the lower temperature side and released at the higher temperature side, leading to an overall heating effect in the conductor.

### Final Answer:
In a metal with a positive Thomson coefficient, when current is passed from the lower temperature to the higher temperature side, heat will be absorbed from the lower temperature side.