Question

What is the unit of electrical conductance?
1. Watt (W)
2. ohm meter (Ω m)
3. ohm`^-1 or mho
4. Siemens/meter

Answer 1

Correct Answer - Option 3 : ohm`^-1 or mho

CONCEPT:

• Resistance (R): Resistance of a conductor opposes the flow of electric current.

R = (ρ × L) / A

Where R = resistance of a conductor; ρ = resistivity of a conductor; L = length of a conductor; A = cross-section area of a conductor

• SI unit of resistance is the ohm (Ω).
• Resistivity (ρ): Resistivity of a material is defined as the property of material how strongly it resists the flow of electric current inside the conductor.

ρ = (R × A)/L

• SI unit of resistivity is the ohm-meter (Ω m)
• Electrical Conductivity (σ): Electrical conductivity is defined as the ability of a conductor to conduct electricity. It is the reciprocal of resistivity.

σ = 1/ρ  

σ = siemens / m

• SI unit of conductivity is the ohm^-1 m^-1 or siemens / m (S/m)

​EXPLANATION:

• SI unit of energy is the watt (W)
• SI unit of resistivity is ohm m (Ω m)
• SI unit of conductance is ohm^-1 (mho)

​Hence option 3 is correct.

•  Conductance (G) is defined as the reciprocal of resistance.
• Its SI unit is mho or ohm^-1.

G = 1/R