The specific resistance of a conductor increases with:

Options

A. increase in temperature
B. increase in cross-sectional area
C. decrease in length
D. decrease in cross-sectional area

Answer

To solve the question regarding the specific resistance of a conductor and how it changes with various factors, we need to analyze the relationship between specific resistance (ρ) and the factors mentioned in the options.

### Step-by-Step Solution:

1. **Understanding Specific Resistance**:
Specific resistance (ρ), also known as resistivity, is a property of a material that quantifies how strongly it resists the flow of electric current. It is defined as:
\[ R = \rho \frac{L}{A} \]
where R is resistance, L is the length of the conductor, and A is its cross-sectional area.

2. **Analyzing the Factors**:
- **Temperature**: As temperature increases, the thermal agitation of the atoms in the conductor increases. This leads to more collisions between the conduction electrons and the vibrating atoms, which increases the resistance. Therefore, specific resistance increases with temperature.
- **Cross-sectional Area (A)**: According to the formula, resistance is inversely proportional to the cross-sectional area. If the area increases, the resistance decreases, which means specific resistance does not increase with an increase in cross-sectional area.
- **Length (L)**: Resistance is directly proportional to the length of the conductor. If the length increases, the resistance increases, but this does not directly affect the specific resistance in the context of the material properties.
- **Decrease in Cross-sectional Area**: A decrease in cross-sectional area leads to an increase in resistance, but again, this does not directly affect the specific resistance as a material property.

3. **Conclusion**:
The specific resistance of a conductor increases primarily with an increase in temperature. Therefore, the correct answer is:
- **Option A: Increase in temperature**.

### Final Answer:
The specific resistance of a conductor increases with an increase in temperature.

---