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Capacitors in AC Circuits quiz

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  • What is the formula for the voltage across a capacitor in an AC circuit?
    The voltage across a capacitor is the charge on the capacitor divided by its capacitance, or V = Q/C.
  • How does the voltage across a capacitor relate to the current in an AC circuit?
    The voltage across a capacitor lags the current by 90 degrees in an AC circuit.
  • What is the mathematical expression for capacitive reactance?
    Capacitive reactance is given by Xc = 1/(omega × capacitance).
  • What is omega in the context of AC circuits?
    Omega is the angular frequency and is calculated as omega = 2π × frequency.
  • How do you calculate the maximum current in a circuit with a capacitor?
    The maximum current is the maximum voltage across the capacitor divided by the capacitive reactance, Imax = Vmax/Xc.
  • What are the units of capacitive reactance?
    Capacitive reactance is measured in ohms, just like resistance.
  • What does it mean when voltage 'lags' current in a capacitor?
    It means the voltage reaches its peak value a quarter cycle after the current does.
  • How does the voltage function for a capacitor differ from that of a resistor in AC circuits?
    The voltage across a capacitor is shifted by -π/2 (or -90 degrees) compared to the voltage across a resistor.
  • What is the relationship between charge and current in a capacitor in AC circuits?
    The charge on the capacitor and the current in the circuit are proportional, but their time functions are out of phase.
  • What is the formula for angular frequency in terms of linear frequency?
    Angular frequency omega is omega = 2π × f, where f is the linear frequency.
  • How do you find the capacitive reactance for a 100 microfarad capacitor at 60 Hz?
    Capacitive reactance is Xc = 1/(omega × C), which equals 26.5 ohms for these values.
  • What is the maximum voltage across a capacitor connected directly to an AC power source?
    The maximum voltage across the capacitor is equal to the maximum voltage of the power source.
  • What is the phase difference between current and voltage in a capacitor in AC circuits?
    The phase difference is 90 degrees, with voltage lagging current.
  • What does capacitive reactance represent in an AC circuit?
    Capacitive reactance acts like resistance, opposing the flow of current in the circuit.
  • How is Ohm's law adapted for capacitors in AC circuits?
    Ohm's law for capacitors uses capacitive reactance: V = I × Xc, where Xc is the capacitive reactance.