### Capacitive Circuits Alternating Currents

# Concepts to remember on the “Capacitive Circuits- Alternating Currents” for JEE and CBSE board exams:

**Capacitors and Capacitance:**

**Capacitance:**The ability of a capacitor to store electrical charge. Measured in farads (F).**Capacitors in AC circuits:**Capacitors oppose the changes in voltage and allow the flow of alternating current.**Charging and discharging of capacitors in AC circuits:**Capacitors charge and discharge alternately during each cycle of AC.

**Reactance and Impedance:**

**Inductive reactance (XL):**Opposition to the flow of AC due to inductance. Measured in ohms.**Capacitive reactance (XC):**Opposition to the flow of AC due to capacitance. Measured in ohms.**Impedance (Z):**Combination of resistance (R), inductive reactance (XL), and capacitive reactance (XC). Measured in ohms.**Phase difference:**Difference in the timing between voltage and current waveforms in AC circuits.

**Power and Power Factor:**

**Average power:**The amount of power delivered or consumed in an AC circuit over a complete cycle. Measured in watts (W).**Reactive power:**The power that flows back and forth between the source and the circuit, not contributing to actual work. Measured in volt-amperes reactive (VAR).**Power factor (PF):**The ratio of average power to apparent power (combination of average power and reactive power). Ranges from 0 to 1.**Power factor correction methods:**Techniques to improve the power factor, such as using capacitors or synchronous condensers.

**Resonant Circuits:**

**Resonance:**Condition when the inductive reactance (XL) and capacitive reactance (XC) cancel each other out, resulting in maximum current flow.**Resonant frequency (f_r):**The frequency at which resonance occurs.**Series resonant circuit:**A circuit with inductance (L) and capacitance (C) connected in series.**Parallel resonant circuit:**A circuit with inductance (L) and capacitance (C) connected in parallel.**Quality factor (Q-factor):**Measure of the sharpness of resonance, indicating the energy storage capacity of the circuit.

**AC Generators and Transformers:**

**AC generators:**Convert mechanical energy into electrical energy by rotating a coil in a magnetic field.**Emf equation:**E = Blv, where E is the emf generated, B is the magnetic field strength, l is the length of the conductor, and v is the velocity of the conductor.**Frequency:**Number of cycles per second in an AC waveform. Measured in hertz (Hz).**Transformers:**Transfer electrical energy from one circuit to another through electromagnetic induction.**Turns ratio:**Ratio of the number of turns in the primary coil to the number of turns in the secondary coil.**Voltage and current transformation:**Voltage and current in the secondary coil are directly proportional to the turns ratio.