Question 1

What is a capacitor?

Accepted Answer

A capacitor is an electrical component that stores electrical energy in an electric field. It consists of two conductive plates separated by an insulating material (dielectric). Capacitors are used in circuits for energy storage, filtering, timing, and signal coupling applications.

Question 2

How do you calculate capacitor charge?

Accepted Answer

Capacitor charge is calculated using the formula Q = C × V, where Q is the charge in coulombs, C is the capacitance in farads, and V is the voltage across the capacitor. This relationship shows that charge is directly proportional to both capacitance and voltage.

Question 3

What is the energy stored in a capacitor?

Accepted Answer

The energy stored in a capacitor is calculated using E = ½ × C × V², where E is the energy in joules, C is the capacitance, and V is the voltage. This energy is stored in the electric field between the capacitor plates and can be released when the capacitor discharges.

Question 4

How do you calculate capacitive reactance?

Accepted Answer

Capacitive reactance is calculated using Xc = 1 / (2πfC), where Xc is the reactance in ohms, f is the frequency in hertz, and C is the capacitance in farads. Capacitive reactance decreases as frequency increases, making capacitors act like short circuits at high frequencies.

Question 5

What is the time constant of an RC circuit?

Accepted Answer

The time constant (τ) of an RC circuit is calculated using τ = R × C, where R is the resistance in ohms and C is the capacitance in farads. The time constant represents the time it takes for the capacitor to charge to 63.2% of the applied voltage or discharge to 36.8% of its initial voltage.

Question 6

How do capacitors behave in AC circuits?

Accepted Answer

In AC circuits, capacitors create a phase shift between voltage and current. The current leads the voltage by 90 degrees. Capacitors block DC current but allow AC current to pass, with the amount of current depending on the frequency and capacitive reactance.

Question 7

What are the units of capacitance?

Accepted Answer

The SI unit of capacitance is the farad (F). Common submultiples include microfarads (μF = 10⁻⁶ F), nanofarads (nF = 10⁻⁹ F), and picofarads (pF = 10⁻¹² F). Most practical capacitors are measured in microfarads or picofarads.

Question 8

How do you calculate capacitor current?

Accepted Answer

Capacitor current is calculated using I = C × dV/dt, where I is the current, C is the capacitance, and dV/dt is the rate of change of voltage with respect to time. In DC circuits, once fully charged, the current becomes zero. In AC circuits, current depends on frequency and voltage amplitude.

Question 9

What is the difference between series and parallel capacitors?

Accepted Answer

In series, the total capacitance is less than the smallest individual capacitor: 1/Ctotal = 1/C1 + 1/C2 + ... In parallel, the total capacitance is the sum of individual capacitances: Ctotal = C1 + C2 + ... Series capacitors share the same charge, while parallel capacitors share the same voltage.

Question 10

How are capacitors used in practical applications?

Accepted Answer

Capacitors are used in power supplies for filtering, in timing circuits for delays, in audio circuits for coupling, in motor starting applications, in power factor correction, and in electronic devices for energy storage. They're essential components in virtually all electronic circuits.

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