The "rho formula" refers to the formula for calculating resistivity, represented by the Greek letter rho (ρ). Resistivity is a fundamental property of a material that quantifies how strongly it opposes the flow of electric current.
The Resistivity Formula (ρ)
According to the reference, the formula to calculate resistivity (ρ) is:
ρ = RA / l
Where:
- ρ (rho) is the resistivity (measured in ohm-meters, Ω⋅m)
- R is the resistance (measured in ohms, Ω)
- A is the cross-sectional area of the material (measured in square meters, m2)
- l is the length of the material (measured in meters, m)
Understanding Resistivity
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Definition: Resistivity is an intrinsic property of a material that describes its opposition to the flow of electric current. Unlike resistance, which depends on the object's size and shape, resistivity is a material constant.
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Units: The SI unit for resistivity is the ohm-meter (Ω⋅m).
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Factors Affecting Resistivity: Resistivity depends on the material's atomic structure and temperature.
Applying the Formula: Example
Imagine a copper wire with:
- Resistance (R) = 2 ohms
- Length (l) = 10 meters
- Cross-sectional area (A) = 0.000002 square meters (2 x 10-6 m2)
Using the resistivity formula:
ρ = (2 ohms * 0.000002 m2) / 10 m
ρ = 0.0000004 Ω⋅m or 4 x 10-7 Ω⋅m
This calculation gives us the resistivity of the copper wire.
