Comparison of Resistor, Capacitor, and Inductor
| Feature | Resistor | Capacitor | Inductor |
|---|---|---|---|
| Symbol | R | C | L |
| Unit | Ohms (Ω) | Farads (F) | Henries (H) |
| Function | Opposes current flow by converting electrical energy to heat. | Stores energy in an electric field. | Stores energy in a magnetic field. |
| Construction | Made of materials like carbon or metal wire wound into a coil. | Consists of two conductive plates separated by an insulating material (dielectric). | Consists of a wire coil, sometimes wrapped around a magnetic core. |
| Circuit Representation | ![]() |
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| Voltage-Current Relationship | V = IR (Ohm's Law) | I = C(dV/dt) | V = L(dI/dt) |
| Frequency Response (AC) | Impedance is constant, independent of frequency. | Impedance decreases with increasing frequency. | Impedance increases with increasing frequency. |
| Behavior in DC Circuits | Resistance is constant, opposes current flow. | Acts as an open circuit after fully charging. | Acts as a short circuit when DC is applied. |
| Behavior in AC Circuits | Resists current without changing its phase. | Creates a phase shift of -90° between voltage and current. | Creates a phase shift of +90° between voltage and current. |
| Energy Dissipation | Energy is dissipated as heat. | Stores energy, no dissipation. | Stores energy, no dissipation. |
| Applications | Current limiting, voltage division, heating. | Filtering, coupling/decoupling in circuits. | Used in transformers, filters, and oscillators. |
| Real-World Devices | Heating elements, voltage dividers, resistive touchscreens. | Power supply filtering, timing circuits, audio crossovers. | Transformers, motors, inductive sensors, chokes. |
Comparison Between Capacitive Reactance and Inductive Reactance
| Property | Capacitive Reactance (Xc) | Inductive Reactance (Xl) |
|---|---|---|
| Definition | Capacitive reactance is the opposition to the change in voltage across a capacitor in an AC circuit. | Inductive reactance is the opposition to the change in current through an inductor in an AC circuit. |
| Formula | Xc = 1 / (2Ï€fC) | Xl = 2Ï€fL |
| Unit | Ohms (Ω) | Ohms (Ω) |
| Dependence | Capacitive reactance is inversely proportional to frequency (f) and capacitance (C). | Inductive reactance is directly proportional to frequency (f) and inductance (L). |
| Phase Relationship | In a capacitive circuit, current leads voltage by 90° (current is ahead of voltage). | In an inductive circuit, current lags behind voltage by 90° (current is behind voltage). |
| Behavior at Low Frequency | At low frequencies, capacitive reactance is high (Xc → ∞), which blocks current. | At low frequencies, inductive reactance is low (Xl → 0), which allows more current to flow. |
| Behavior at High Frequency | At high frequencies, capacitive reactance is low (Xc → 0), which allows more current to flow. | At high frequencies, inductive reactance is high (Xl → ∞), which blocks current. |
| Power Dissipation | No real power is dissipated; energy is stored and released in the electric field of the capacitor. | No real power is dissipated; energy is stored and released in the magnetic field of the inductor. |
| Application | Used in tuning circuits, filters, and reactive power compensation in AC systems. | Used in transformers, motors, and filters in AC systems. |
Mathematical Analysis
Capacitive and inductive reactance are key components in AC circuits that affect how voltage and current behave, influencing the overall impedance of the circuit. They play an important role in phase angle shifts and impedance matching.
Capacitive Reactance (Xc):
Capacitive reactance decreases as frequency increases, making it easier for current to pass through the capacitor:
Xc = 1 / (2Ï€fC)
Where:
- Xc = Capacitive Reactance (Ohms, Ω)
- f = Frequency of AC signal (Hertz, Hz)
- C = Capacitance (Farads, F)
Inductive Reactance (Xl):
Inductive reactance increases as frequency increases, making it harder for current to pass through the inductor:
Xl = 2Ï€fL
Where:
- Xl = Inductive Reactance (Ohms, Ω)
- f = Frequency of AC signal (Hertz, Hz)
- L = Inductance (Henries, H)


