Correct Answer

Concept & PrincipleElectricalBasic Electrical

Option A

Quick Summary: In a purely inductive circuit, the current lags behind the applied voltage by an angle of $90^\circ$. Since the power factor is defined as the cosine of the phase angle difference between voltage and current, $\cos(90^\circ) = 0$.

💡 Explanation

In a purely inductive circuit, the current lags behind the applied voltage by an angle of $90°$ . Since the power factor is defined as the cosine of the phase angle difference between voltage and current, $\cos(90°) = 0$ .

🔢 Key Formulas

$P = VI \cos(\phi)$ — Formula for real power

$\phi = 90°$ — Phase angle for pure inductor

⚙️ Working Principle

In an ideal inductor, the voltage $v(t) = L \frac{di}{dt}$ leads the current by $90°$ because the opposition to change in current is purely reactive. As there is no resistance, no real power is dissipated (true power is zero), and the entirety of the energy oscillates between the source and the inductor's magnetic field. This phase shift of $\pi/2$ radians results in a power factor of zero, characterizing the circuit as purely reactive.

📌 Key Points

▸
Pure inductor consumes zero real power (Active Power P = 0).
▸
It only exchanges reactive power (VAR) with the supply.
▸
The power factor is always lagging in inductive circuits.
▸
The current is purely reactive, represented as $I = I_m \sin(\omega t - 90°)$ .

✅ Advantages

▸
Used in energy storage (magnetic field).
▸
Fundamental building block for filters and oscillators.

❌ Disadvantages / Limitations

▸
Causes lagging power factor in transmission lines.
▸
Increases current requirement for a given real power demand.

🛠️ Applications / Uses

▸
Induction motors
▸
Transformers
▸
Chokes in fluorescent lighting

📄 Additional Information

▸
Option B (1) represents a purely resistive circuit.
▸
Option C ( $\infty)$ is physically impossible for power factor.
▸
The range of power factor is always between 0 and 1.

📊 Diagram / Illustration

✅

A is correct — The phase difference between voltage and current in a pure inductor is $90°$ , leading to a power factor of $\cos(90°) = 0$ .

Core Concepts Used

Click any tag to open in AI Tutor

Reactive Power Phase Angle Inductive Reactance

💡 EXAM TIP

Remember: 'ELI the ICE man'. ELI means in an Inductor (L), current (I) lags voltage (E). ICE means in a Capacitor (C), current (I) leads voltage (E).

Discussion (0)

Loading discussion...

Prev Next

Correct Answer

Related Questions

Discussion (0)