The unit of specific resistance is

Options

A. ohm
B. ohm
C. ohm-metre
D. ohm per metre

Answer

To determine the unit of specific resistance, we can follow these steps:

### Step 1: Understand Specific Resistance
Specific resistance, also known as resistivity, is a property of materials that quantifies how strongly they resist the flow of electric current. It is denoted by the symbol ρ (rho).

### Step 2: Recall the Formula for Resistance
The resistance \( R \) of a material can be expressed using the formula:
\[ R = \rho \frac{L}{A} \]
where:
- \( R \) is the resistance in ohms (Ω),
- \( \rho \) is the specific resistance (resistivity) in ohm-meters (Ω·m),
- \( L \) is the length of the conductor in meters (m),
- \( A \) is the cross-sectional area of the conductor in square meters (m²).

### Step 3: Analyze the Units
From the formula, we can rearrange it to express specific resistance:
\[ \rho = R \frac{A}{L} \]
Here, \( R \) has units of ohms (Ω), \( A \) has units of square meters (m²), and \( L \) has units of meters (m).

### Step 4: Substitute the Units
Substituting the units into the equation for specific resistance gives:
\[ \text{Units of } \rho = \text{Units of } R \times \frac{\text{Units of } A}{\text{Units of } L} \]
\[ \text{Units of } \rho = \Omega \times \frac{m^2}{m} \]
\[ \text{Units of } \rho = \Omega \times m \]
Thus, the unit of specific resistance is ohm-meter (Ω·m).

### Conclusion
The unit of specific resistance is **ohm-meter (Ω·m)**.

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