Siemens is the unit of ______.
Understanding the Siemens Unit in Physics
The question asks about the physical quantity for which Siemens is the standard unit. We are given options including electric conductance, permittivity, watt per steradian, and permeability. Let's examine each option to determine the correct association for the Siemens unit.
What is Electric Conductance?
Electric conductance is a measure of how easily electric current flows through a material. It is the reciprocal of electrical resistance. The symbol commonly used for electric conductance is \(G\).
The relationship between conductance \(G\) and resistance \(R\) is given by the formula:
where \(R\) is measured in Ohms (\(\Omega\)).
The unit of electric conductance is the Siemens (symbol: S). This unit is named after Werner von Siemens.
Evaluating Other Options and Their Units
Let's briefly look at the other options to understand why Siemens is not their unit:
- Permittivity: Permittivity (\(\epsilon\)) is a measure of how an electric field affects, and is affected by, a dielectric medium. It describes the amount of electric field generated per unit charge in a medium. The unit of permittivity is the Farad per meter (F/m).
- Watt per steradian: Watt per steradian (W/sr) is the unit of radiant intensity, which is the power emitted by a point source in a specific direction per unit solid angle. This unit is related to radiation and optics, not typically electrical properties in the same context as conductance.
- Permeability: Permeability (\(\mu\)) is a measure of the degree of magnetization of a material that responds linearly to an applied magnetic field. It describes the amount of magnetic field generated per unit current in a medium. The unit of permeability is the Henry per meter (H/m).
Summary of Units
To clarify, here is a table summarizing the units for the discussed quantities:
| Quantity | Symbol | Unit | Unit Symbol |
|---|---|---|---|
| Electric Conductance | \(G\) | Siemens | S |
| Electrical Resistance | \(R\) | Ohm | \(\Omega\) |
| Permittivity | \(\epsilon\) | Farad per meter | F/m |
| Radiant Intensity | \(I_\text{e}\) | Watt per steradian | W/sr |
| Permeability | \(\mu\) | Henry per meter | H/m |
From this analysis, it is clear that the Siemens is the unit of electric conductance.
Revision Table: Key Electrical Concepts
| Concept | Definition | Unit |
|---|---|---|
| Electric Conductance | Ease with which electric current flows | Siemens (S) |
| Electrical Resistance | Opposition to electric current flow | Ohm (\(\Omega\)) |
| Conductivity | Ability of a material to conduct electric current (intensive property) | Siemens per meter (S/m) |
| Resistivity | Opposition of a material to electric current flow (intensive property) | Ohm-meter (\(\Omega \cdot \text{m}\)) |
Additional Information on Siemens and Conductance
The Siemens unit was adopted by the International Electrotechnical Commission (IEC) in 1935 and by the General Conference on Weights and Measures (CGPM) in 1971. Before the adoption of the Siemens, the unit for conductance was sometimes referred to as the 'mho' (Ohm spelled backwards), represented by the symbol \(\mho\). The mho is now obsolete, and Siemens is the standard SI unit.
Conductance is a useful concept in analyzing parallel circuits, where conductances simply add up, similar to how resistances add up in series circuits.
While conductance is for a specific component, conductivity is an intrinsic material property, indicating how well a substance conducts electricity. Conductivity (\(\sigma\)) is the reciprocal of resistivity (\(\rho\)), and its unit is Siemens per meter (S/m).
\(\sigma = \frac{1}{\rho}\)
Conductance \(G\) is related to conductivity \(\sigma\) by the geometry of the conductor (e.g., length \(L\) and cross-sectional area \(A\)):
\(G = \sigma \frac{A}{L}\)
This shows how the material property (conductivity) relates to the property of a specific object (conductance).
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The deluge affected the population.The major source of vitamins and minerals for vegetarians is
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1. The Commission did not hold enquiries in the districts which were not affected.
2. The Commission did record the statements of ryots, sahukars and eye-witnesses.
Select the correct answer using the code given below:
