Physics · Class 12 · Chapter 7
Alternating Current
10 lessons88 min7 simulations10 practice questions
The mains supply alternates, so this chapter works out how resistors, inductors and capacitors behave when the voltage across them follows a sine curve. It introduces rms values so that ac power looks like dc power, uses rotating phasors to track phase, defines reactance and impedance, finds the resonance of a series LCR circuit, shows why only the in-phase part of the current uses power, and ends with the transformer that makes ac the choice for power supply.
Also called: AC circuits · LCR circuit · resonance · transformer
Lessons
10 lessons · 88 min
01Alternating voltage and a resistorNCERT §7.1, §7.25 min02RMS values and average powerNCERT §7.29 min1 sim03PhasorsNCERT §7.35 min04AC through an inductorNCERT §7.48 min1 sim05AC through a capacitorNCERT §7.510 min1 sim06Series LCR circuit and impedanceNCERT §7.6, §7.6.19 min1 sim07ResonanceNCERT §7.6.29 min1 sim08Power factorNCERT §7.79 min1 sim09TransformersNCERT §7.89 min1 sim10Chapter reviewMust-know facts, traps and formulas15 min
Simulations
7 in this chapter
Why 220 V mains peaks at 311 VIn: RMS values and average powerWhich leads: V or I?In: AC through an inductorReactance of a coil and a capacitorIn: AC through a capacitorAdding the voltages in a series LCR circuitIn: Series LCR circuit and impedanceTuning a series LCR circuitIn: ResonancePower factor: where does the power go?In: Power factorAn ideal transformerIn: Transformers