In a dry cell, the positive terminal is the metal cap on the carbon rod. Let's understand why this is the case.

1. Understanding the components of a dry cell:
- A dry cell consists of two electrodes, an electrolyte, and a casing.
- The two electrodes are the carbon rod (negative terminal) and a metal cap (positive terminal).
- The electrolyte is a paste-like mixture containing manganese dioxide and powdered carbon.
- The casing is typically made of zinc and serves as the container for the cell.

2. Role of the carbon rod:
- The carbon rod acts as the negative terminal in a dry cell.
- It is made of graphite, a form of carbon that conducts electricity.
- The carbon rod provides a pathway for the flow of electrons during the cell's operation.

3. Role of manganese dioxide:
- Manganese dioxide is a compound that serves as an oxidizing agent in the dry cell.
- It reacts with the carbon rod to facilitate the movement of electrons.
- The reaction between manganese dioxide and carbon rod creates a flow of electrons from the carbon rod to the metal cap.

4. Role of powdered carbon:
- Powdered carbon is mixed with manganese dioxide to form the electrolyte.
- It helps to increase the conductivity of the electrolyte, allowing for better electron flow.

5. Role of the metal cap:
- The metal cap, typically made of brass or another conductive material, acts as the positive terminal.
- It receives the electrons from the carbon rod through the electrolyte.
- The metal cap is connected to the external circuit, allowing the flow of electrons to power devices connected to the cell.

Conclusion:
In a dry cell, the positive terminal is the metal cap on the carbon rod. While the carbon rod and manganese dioxide are essential components for the cell's operation, it is the metal cap that serves as the positive terminal and connects to the external circuit.