Correct Answer

Concept & PrincipleElectricalBasic Electrical

Option B

Voltage

Quick Summary: In an RC series circuit, the total voltage applied to the circuit leads the current by a phase angle $\phi$, where $0

💡 Explanation

In an RC series circuit, the total voltage applied to the circuit leads the current by a phase angle $\phi$ , where $0 < \phi < 90°$ . Consequently, the voltage across the circuit is said to lead, while the current is said to lag the total voltage.

🔢 Key Formulas

$\phi = \tan^{-1}(\frac{X_C}{R})$ — phase angle of the RC circuit

$V = \sqrt{V_R^2 + V_C^2}$ — total voltage in RC series circuit

⚙️ Working Principle

In an ideal capacitor, the current leads the voltage by $90°$ . In a series RC circuit, the resistor voltage is in phase with the current, while the capacitor voltage lags the current by $90°$ . The phasor sum of these two voltages results in a total voltage that is displaced by an angle $\phi$ behind the current, meaning the circuit acts as a capacitive load with a leading power factor (the voltage lags the current).

📌 Key Points

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The current in a capacitor always leads the voltage by $90°$ .
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In a series RC circuit, the net phase shift is determined by the ratio of capacitive reactance $X_C$ to resistance $R$ .
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The power factor of an RC circuit is always leading.

✅ Advantages

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Used in timing circuits and oscillators.
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Effective in filtering applications for noise suppression.

❌ Disadvantages / Limitations

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Energy dissipation occurs in the resistive component.
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Phase shift is frequency dependent.

🛠️ Applications / Uses

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Coupling and decoupling circuits.
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RC low-pass and high-pass filters.

📄 Additional Information

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If the circuit were purely inductive (RL), the voltage would lead the current.
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The phase angle $\phi$ is $90°$ only if $R=0$ (pure capacitor).

📊 Diagram / Illustration

✅

B is correct — In an RC series circuit, the total voltage across the circuit lags behind the current.

Core Concepts Used

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Phasor Algebra Capacitive Reactance Phase Angle

💡 EXAM TIP

Remember 'ELI the ICE man': In an Inductor (L), E leads I; in a Capacitor (C), I leads E.

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