Chapter 7: Alternating Current
NCERT Class 12 Physics, Part I, Chapter 7. 8 lessons, 17 narrated 3D videos, 9 simulations and 16 quiz questions, following the textbook section by section.
- AC voltage across a resistorThe socket in your wall does not give a steady voltage like a cell. Its voltage rises, falls, reverses and comes back, fifty times every second. This is alternating…
- PhasorsDrawing sine curves for every voltage and current gets messy. There is a neater way to show both the size and the timing of an ac quantity: the phasor.
- AC voltage across an inductorConnect an ac source v equals v m sin ωt across a coil of inductance L. Assume the coil’s resistance is negligible: a pure inductor.
- AC voltage across a capacitorConnect a capacitor to a battery. Current flows for a moment while it charges, then stops. In a dc circuit, a capacitor blocks the current.
- The series LCR circuit and resonanceNow put a resistor R, an inductor L and a capacitor C in series with an ac source, v equals v m sin ωt. Because they are in series, the same current i flows through all…
- Power in AC circuits and power factorIn a general ac circuit the source voltage is v equals v m sin ωt, and the current is i equals i m sin of ωt plus φ. How much power does the source deliver on average?
- TransformersYour phone charger turns 220 volts from the socket into a few volts. A power station sends out electricity at hundreds of kilovolts. Both jobs are done by a transformer.
- LC oscillationsThis topic is beyond the current NCERT syllabus, but it is a beautiful idea and it is useful for competitive exams. What happens when a charged capacitor is connected…