Ohm is unit of all of the following except
Capacitance
This question asks us to identify which among the given electrical quantities does NOT have Ohm ($\Omega$) as its unit of measurement. Let's examine the units for each option:
Ohm Unit: Understanding Reactance, Resistance & Capacitance
Electrical circuits involve various quantities, each with a specific unit. The Ohm ($\Omega$) is a fundamental unit, primarily associated with opposition to current flow.
Resistance
Resistance is the property of a material that opposes the flow of electric current. It is defined by Ohm's Law, $V = IR$, where $V$ is voltage, $I$ is current, and $R$ is resistance. The unit of resistance is the Ohm ($\Omega$).
Reactance (Inductive and Capacitive)
In alternating current (AC) circuits, components like inductors and capacitors also offer opposition to current flow. This opposition is called reactance.
- Inductive Reactance ($X_L$): This is the opposition offered by an inductor. It is calculated as $X_L = \omega L$, where $\omega$ is the angular frequency (in radians per second) and $L$ is the inductance (in Henries). Despite depending on inductance, the unit of inductive reactance is also the Ohm ($\Omega$).
- Capacitive Reactance ($X_C$): This is the opposition offered by a capacitor. It is calculated as $X_C = \frac{1}{\omega C}$, where $\omega$ is the angular frequency and $C$ is the capacitance (in Farads). Similar to inductive reactance, the unit of capacitive reactance is the Ohm ($\Omega$).
Both inductive and capacitive reactance are measures of impedance in AC circuits and are measured in Ohms.
Capacitance
Capacitance is the ability of a component (like a capacitor) to store electrical energy in an electric field. It measures how much charge is stored per unit of voltage. The unit of capacitance is the Farad (F).
Unit Comparison Table
| Electrical Quantity | Symbol | Unit | Unit Symbol |
|---|---|---|---|
| Resistance | $R$ | Ohm | $\Omega$ |
| Inductive Reactance | $X_L$ | Ohm | $\Omega$ |
| Capacitive Reactance | $X_C$ | Ohm | $\Omega$ |
| Capacitance | $C$ | Farad | F |
As seen from the table and the explanations, Ohm ($\Omega$) is the unit for Resistance, Inductive Reactance, and Capacitive Reactance. However, Capacitance is measured in Farads (F).
Therefore, Ohm is the unit of all the given options except for Capacitance.
Important Questions from Resistance and Resistivity
Which of the following statements are correct about the electrical resistance and resistivity of a wire?
1. Both quantities depend on the area of cross-section of the wire
2. Both depend on the temperature
3. Resistance of the wire is directly proportional to the resistivity of the wire
4. Resistivity of the wire is directly proportional to the length of the
wireSelect the correct answer using the code given below:
A circular coil of single turn has a resistance of 20 Ω. Which one of the following is the correct value for resistance between the ends of any diameter of the coil?
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A fuse wire must be
