What is the SI unit for electrical resistance? विद्युत प्रतिरोध के लिए SI इकाई क्या है?
Ohm
Understanding Electrical Resistance
Electrical resistance is a measure of how much a material opposes the flow of electric current. When voltage is applied across a component or material, a current flows through it. Resistance determines how much current flows for a given voltage. Higher resistance means less current flows for the same voltage.
SI Units in Physics
The International System of Units (SI) is the modern form of the metric system. It is the world's most widely used system of measurement. It includes base units for fundamental quantities like length, mass, time, electric current, temperature, amount of substance, and luminous intensity. Derived units are then formed from these base units.
Identifying the SI Unit for Electrical Resistance
The SI unit for electrical resistance is named after the German physicist Georg Simon Ohm, who formulated Ohm's Law. Ohm's Law relates voltage (\(V\)), current (\(I\)), and resistance (\(R\)) with the formula \(V = IR\). From this formula, resistance can be expressed as \(R = V/I\).
Let's look at the options provided and what physical quantity their SI unit measures:
| Option | Unit | Physical Quantity |
|---|---|---|
| 1 | Mole | Amount of substance |
| 2 | Kelvin | Thermodynamic temperature |
| 3 | Ampere | Electric current |
| 4 | Ohm | Electrical resistance |
Based on the standard definitions of SI units, the unit specifically designated for electrical resistance is the Ohm.
Analyzing the Options
- Mole: The mole (symbol: mol) is the SI unit of amount of substance. It is used to measure the quantity of entities (like atoms, molecules, ions) in a sample.
- Kelvin: The kelvin (symbol: K) is the SI unit of thermodynamic temperature. It is one of the seven base SI units.
- Ampere: The ampere (symbol: A) is the SI unit of electric current. It is also one of the seven base SI units.
- Ohm: The ohm (symbol: \(\Omega\)) is the SI derived unit of electrical resistance. It is defined as the resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces a current of 1 ampere, the conductor not being the source of any electromotive force.
Therefore, the SI unit for electrical resistance is the Ohm.
Revision Table: Common Electrical Units
| Quantity | SI Unit | Symbol |
|---|---|---|
| Electric Charge | Coulomb | C |
| Electric Current | Ampere | A |
| Voltage / Potential Difference | Volt | V |
| Electrical Resistance | Ohm | \(\Omega\) |
| Electrical Conductance | Siemens | S |
| Electric Power | Watt | W |
| Electrical Energy | Joule | J |
Additional Information on Electrical Resistance
Electrical resistance depends on several factors:
- Material: Different materials have different inherent resistances (resistivity). Conductors like copper have low resistance, while insulators like rubber have very high resistance.
- Length: The resistance of a uniform conductor is directly proportional to its length. Longer wires have higher resistance.
- Cross-sectional Area: The resistance of a uniform conductor is inversely proportional to its cross-sectional area. Thicker wires have lower resistance.
- Temperature: For most conductors, resistance increases with increasing temperature.
The relationship between resistance (\(R\)), resistivity (\(\rho\)), length (\(L\)), and cross-sectional area (\(A\)) is given by the formula:
\(R = \frac{\rho L}{A}\)
This formula is useful for calculating the resistance of a specific piece of material.
Important Questions from The international system of units
- What is the SI unit of the permittivity of free space ($\$ \epsilon_0 \$ $) when expressed in terms of the fundamental SI units (kilogram, meter, second, and ampere)?
The energy value of food is measured in the Unit of
The unit of magnetic dipole moment is
- Which of the following physical quantities has its SI unit defined as one Weber of magnetic flux per Ampere of current ($1 \text{ Wb/A}$), or equivalently, one Volt-second per Ampere ($1 \text{ V}\cdot\text{s/A}$)?
- Which of the following expressions correctly represents the SI derived unit for velocity, utilizing only SI base units?
