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⚛️ Physics  ·  Alternating Current  ·  NEET & JEE

An AC source (V<sub>0</sub> = 100 V) is connected to a 5 Ω resistor. Peak current and RMS current are:

Answer: 20 A peak, 14.14 A RMS.

  • A 20 A peak, 14.14 A RMS
  • B 100 A peak, 70.7 A RMS
  • C 5 A peak, 3.54 A RMS
  • D 10 A peak, 7.07 A RMS

Correct answer: A. 20 A peak, 14.14 A RMS

Explanation: I<sub>0</sub> = V<sub>0</sub>/R = 100/5 = 20 A. I<sub>rms</sub> = I<sub>0</sub>/√2 = 20/1.414 ≈ 14.14 A.

V and I Phase Relationships in AC CircuitsPure Inductor: I lags V by 90°VIPure Capacitor: I leads V by 90°VIMemory aid "ELI the ICE man": in an inductor (L) E(V) leads I; in a capacitor (C) I leads E(V)For a pure resistor, V and I stay perfectly in phase (no lag or lead at all)

In a pure inductor the current lags the voltage by 90° (energy is briefly stored in the magnetic field before current responds); in a pure capacitor the current leads the voltage by 90° (current must flow to build up charge before voltage rises) - the mnemonic "ELI the ICE man" keeps these straight.

Concept context

AC circuits, impedance, LCR series circuit, resonance, transformers, and power factor.

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