Electronics: Capacitors Overview
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Questions and Answers

What is the relationship between the energy stored in a capacitor and the potential difference across it?

  • The energy is inversely proportional to the potential difference.
  • The energy is proportional to the square of the potential difference. (correct)
  • The energy is inversely proportional to the square of the potential difference.
  • The energy is directly proportional to the potential difference.
  • What does the area under a p.d.-charge graph represent?

  • The current flowing through the capacitor.
  • The capacitance of the capacitor.
  • The power dissipated by the capacitor.
  • The work done to charge the capacitor. (correct)
  • If the potential difference across a capacitor is doubled, what happens to the energy stored in the capacitor?

  • It remains the same.
  • It is quadrupled. (correct)
  • It is halved.
  • It is doubled.
  • Which of the following equations is NOT a valid expression for the energy stored in a capacitor?

    <p>W = ½CV²</p> Signup and view all the answers

    A 10 μF capacitor is charged to a potential difference of 100 V. What is the energy stored in the capacitor?

    <p>0.5 J</p> Signup and view all the answers

    A capacitor stores 2 J of energy when the potential difference across it is 10 V. What is the capacitance of the capacitor?

    <p>0.04 F</p> Signup and view all the answers

    What is the equivalent capacitance when two $10 \mu F$ capacitors are connected in series?

    <p>$5 \mu F$</p> Signup and view all the answers

    When capacitors are connected in parallel, which of the following is true?

    <p>The potential difference across each capacitor is the same.</p> Signup and view all the answers

    If two capacitors, with capacitances of $C_1$ and $C_2$ respectively, are connected in series, what is the equivalent capacitance?

    <p>$\frac{C_1 C_2}{C_1+C_2}$</p> Signup and view all the answers

    If three capacitors of $2 \mu F$, $3 \mu F$ and $6 \mu F$ are connected in parallel, what is the total capacitance?

    <p>$11 \mu F$</p> Signup and view all the answers

    Which of the following is true about charge when capacitors are connected in series?

    <p>The charge is the same on all capacitors.</p> Signup and view all the answers

    How does the total capacitance of capacitors in a series circuit compare to the individual capacitances?

    <p>It is always less than the smallest individual capacitance.</p> Signup and view all the answers

    If the charge on a capacitor is doubled, and the capacitance remains constant, how does the energy stored change?

    <p>It quadruples.</p> Signup and view all the answers

    Which of the following statements accurately describes the relationship between capacitance and energy stored when the charge remains constant?

    <p>Energy stored is inversely proportional to capacitance.</p> Signup and view all the answers

    What does the area under the potential difference-charge graph for a capacitor represent?

    <p>The energy stored in the capacitor.</p> Signup and view all the answers

    When a capacitor is being charged, what is the role of the external power supply?

    <p>To provide the work needed to push electrons onto the capacitor plates.</p> Signup and view all the answers

    A capacitor stores 0.5 J of energy when charged to a 10 V potential difference. What happens to the energy stored if the capacitor is charged to 20 V, assuming the capacitance remains constant?

    <p>It becomes 2 J.</p> Signup and view all the answers

    Which of the following best describes the flow of electrons during the charging process of a capacitor?

    <p>Electrons flow from the power source to the negative plate and move from the positive plate to the power source.</p> Signup and view all the answers

    If two capacitors have the same charge, but one has twice the capacitance of the other, how does the energy stored in the capacitors compare?

    <p>The capacitor with twice the capacitance stores half the energy.</p> Signup and view all the answers

    In the experimental setup, why does the ammeter reading settle to zero after initially registering a current when the switch is closed?

    <p>The capacitors become fully charged, blocking further current flow.</p> Signup and view all the answers

    According to the results, what can cause the difference in calculated charges ($Q_1$ and $Q_2$)?

    <p>Variations in the voltmeter readings and capacitor manufacturing tolerances.</p> Signup and view all the answers

    In the first row of Table 1, what is the ratio of $Q_1$ to $Q_2$?

    <p>1:1</p> Signup and view all the answers

    If the voltage across the 500 µF capacitor is measured to be 3.00 V, what is the stored charge, in micro Coulombs?

    <p>1500 µC</p> Signup and view all the answers

    According to the data in the table, which statement is most accurate for this serial circuit?

    <p>The charge on the two capacitors is roughly the same, even with different voltages.</p> Signup and view all the answers

    Why is a resistor included in the circuit?

    <p>To protect the ammeter from large initial currents.</p> Signup and view all the answers

    What is the most appropriate unit for measuring the charge stored on a capacitor in this experiment?

    <p>Micro Coulombs (µC)</p> Signup and view all the answers

    In the circuit diagram, if the 500 µF capacitor was replaced by a 250 µF capacitor, and the voltage across a 1000 µF remained the same as the row 2 values, what would happen to the charge on the 250 µF capacitor ($Q_1$)?

    <p>$Q_1$ would be approximately half of its value in the second row.</p> Signup and view all the answers

    With reference to the ammeter, what is the main difference between the instant the switch is closed, versus when the circuit has reached its steady state?

    <p>The ammeter shows a maximum current reading at the instant the circuit is closed, but zero after stead-state.</p> Signup and view all the answers

    How does changing the power supply's voltage affect the charge stored on the capacitors?

    <p>Increasing the voltage increases the charge stored.</p> Signup and view all the answers

    Study Notes

    Learning Outcomes

    • Demonstrate knowledge, understanding, and application of:
      • total capacitance of capacitors in series,
      • total capacitance of capacitors in parallel,
      • analysis of circuits containing capacitors
      • investigation of circuits containing capacitors.

    Connecting Capacitors

    • Supercapacitors are compact specialist capacitors with capacitance values in the thousands of farads.
    • They are used as alternatives to battery packs, memory backup devices, and emergency lighting.
    • Unlike rechargeable batteries, supercapacitors can be charged over and over again.
    • You are unlikely to have such capacitors in your laboratory.
    • However, if you wanted a particular value, you would need an enormous number of capacitors.

    Capacitors in Parallel

    • Figure 1 shows two capacitors of capacitances C₁ and C₂ connected in parallel.
    • Together, their capacitance is greater than their individual capacitances, so the combination will store more charge for a given potential difference (p.d.).
    • For two or more capacitors in parallel:
      • The p.d. V across each capacitor is the same.
      • Electrical charge is conserved. The total charge stored by the combination is the sum of the individual charges stored by the capacitors, Q = Q₁ + Q₂ + ....
      • The total capacitance C is the sum of the individual capacitances of the capacitors, C = C₁ + C₂ + ....

    Capacitors in Series

    • Figure 2 shows two capacitors of capacitances C₁ and C₂ connected in series.
    • Together, their capacitance is less than their individual capacitances.
    • All the capacitors in series store the same charge. This is even true when they have different capacitances.
    • The cell is connected to the left-hand plate of the capacitor of capacitance C₁ and to the right-hand plate of the capacitor of capacitance C₂.

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    Description

    This quiz covers the fundamentals of capacitors, including total capacitance in series and parallel configurations, and the analysis of circuits containing capacitors. Explore concepts related to supercapacitors and their applications, as well as practical circuit investigations.

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