SI unit of resistivity is

Options

A. ohm metre
B. ohm metre`""^(-1)`
C. ohm metre`""^(-2)`
D. none of these

Explanation

To find the SI unit of resistivity, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Resistivity**:
Resistivity (ρ) is defined as the resistance (R) offered by a material per unit length (L) for a unit cross-sectional area (A). The formula for resistivity can be expressed as:
\[ \rho = \frac{R \cdot A}{L} \]

2. **Identify the Units**:
- The unit of resistance (R) is Ohm (Ω).
- The unit of area (A) is square meters (m²).
- The unit of length (L) is meters (m).

3. **Substituting Units into the Formula**:
We can substitute the units into the resistivity formula:
\[ \rho = \frac{R \cdot A}{L} \implies \rho = \frac{\Omega \cdot m^2}{m} \]

4. **Simplifying the Units**:
When we simplify the units, we notice that one meter (m) in the denominator cancels with one meter in the numerator:
\[ \rho = \Omega \cdot m \]

5. **Final Result**:
Therefore, the SI unit of resistivity is:
\[ \rho = \Omega \cdot m \]
This can also be read as "Ohm-meter".

### Conclusion:
The SI unit of resistivity is Ohm-meter (Ω·m).