Capacitors

    Cards (57)

    • What is the simplest arrangement of a capacitor?
      Two parallel metal plates separated by an insulator
    • What materials typically make up the metal plates and insulator of a capacitor?
      Thin metal foil and plastic or waxed paper
    • What is the primary function of a capacitor?
      To store energy in an electric field
    • What does charging a capacitor involve?
      Building electric charges of equal magnitude but opposite polarity
    • How is capacitance defined mathematically?
      Capacitance is charge stored per volt
    • What is the formula for capacitance?
      C = Q/V
    • What does the symbol 'C' represent in the formula C = Q/V?
      Capacitance measured in Farads
    • What is the unit of capacitance?
      Farads (F)
    • Why are microfarads (μF) and picofarads (pF) more commonly used than Farads?
      Because Farads is a very large unit
    • What happens to the potential difference (pd) when electric charge is stored on the plates of a capacitor?
      The pd between the plates rises
    • What is the relationship between capacitance and charge in parallel capacitors?
      • The pd across each capacitor is the same
      • Total charge is the sum of individual charges
      • Total capacitance is the sum of individual capacitances: CT = C₁ + C₂ + C₃
    • What is the relationship between capacitance and charge in series capacitors?
      • The charge on each capacitor is the same
      • The total potential difference is the sum of individual voltages: V = V₁ + V₂ + V₃
      • Total capacitance is given by: 1/CT = 1/C₁ + 1/C₂
    • How is the energy stored in a charged capacitor calculated?
      Energy is calculated as W = QV
    • What does the term 'discharging' refer to in capacitors?
      Releasing stored energy from the capacitor
    • What is the time constant in a capacitor circuit?
      Time taken for voltage/current to fall to 37% of initial value
    • How is the time constant calculated?
      It is the product of capacitance and resistance
    • What is the formula for the discharging current of a capacitor?
      I = I₀ e<sup>-t/τ</sup>
    • What does the symbol 'e' represent in the discharging current formula?
      The exponential constant, approximately 2.718
    • How does the voltage across a capacitor change during discharging?
      Voltage decreases exponentially
    • What is the formula for the charge stored in a capacitor during discharging?
      Q = Q₀ e<sup>-t/τ</sup>
    • How can the initial voltage (V₀) of a capacitor be determined?
      By using the emf of the battery or power supply
    • How can the initial charge (Q₀) of a capacitor be calculated?
      Q₀ = CV₀
    • How can the initial current (I₀) of a capacitor be calculated?
      I₀ = V₀/R
    • What are the applications of capacitors in medical and photography fields?
      1. Defibrillators:
      • Deliver controlled shocks to restore heart rhythm
      • Store electric charge in an electric field
      1. Camera flashes:
      • Store energy to produce intense light
      • Discharge energy quickly through flash bulb
    • What happens when a capacitor is fully charged?
      It discharges through a resistor
    • How does the charging process of a capacitor occur?
      Electrons flow onto one plate, repelling electrons from the other
    • What role does a resistor play in the discharging of a capacitor?
      It slows the rate of discharge
    • What is the effect of resistance on the current during discharging?
      Current decreases over time
    • How does the voltage across a capacitor behave during charging?
      It gradually increases until fully charged
    • What is the significance of the 37% value in capacitor circuits?
      It represents the time constant for voltage/current decay
    • What is the formula for calculating the time constant (τ) in RC circuits?
      τ = RC
    • How can the time constant be measured in a circuit?
      By plotting ln(I) against time
    • What does the slope of the line in the ln(I) vs. time plot represent?
      The negative reciprocal of the time constant
    • What is the relationship between the charge flow and the electric current in a capacitor?
      Charge flow constitutes an electric current
    • What happens to the voltage across a resistor when a capacitor discharges?
      It follows the current curve due to Ohm's law
    • How does the initial charge affect the charging process of a capacitor?
      It determines the amount of charge transferred
    • What is the role of the power supply in charging a capacitor?
      It provides the voltage needed for charging
    • What happens to the charge on the plates of a capacitor when it is fully charged?
      The charge remains until discharged
    • How does the resistance in a circuit affect the time constant?
      Higher resistance increases the time constant
    • What is the effect of capacitance on the charging time of a capacitor?
      Larger capacitance results in longer charging time