Question 1

How is energy stored in a capacitor?

Accepted Answer

Energy stored in a capacitor is determined by integrating the instantaneous power delivered to it over time. This energy is expressed in terms of charge and capacitance, representing the energy present in the electric field between the plates. An ideal capacitor does not dissipate this energy, allowing it to be fully retrieved when needed.

Question 2

Why does a capacitor have memory?

Accepted Answer

Capacitors possess memory because their voltage at any moment depends on the past flow of current through them. This property allows capacitors to remember their charging and discharging history, making them useful in applications such as memory storage in computers and signal processing circuits.

Question 3

What happens when a capacitor is connected to a battery?

Accepted Answer

When connected to a battery, a parallel plate capacitor develops a potential difference across its plates. This potential difference determines how much electrical energy the capacitor can store. The voltage across the capacitor increases over time according to an equation derived from integrating the voltage-current relationship.

Question 4

Can the voltage across a capacitor change instantly?

Accepted Answer

No, the voltage across a capacitor is always continuous and cannot change abruptly. This behavior is essential in many applications, such as smoothing out voltage in power supplies and filtering out noise in signal processing. This property ensures stable operation in electronic circuits.

Question 5

How do ideal and non-ideal capacitors differ in energy storage?

Accepted Answer

An ideal capacitor does not dissipate energy, so all stored energy can be retrieved. A non-ideal capacitor has a parallel-model leakage resistance that causes some energy loss. However, this leakage resistance is usually high enough to be neglected in most practical applications, making non-ideal capacitors behave nearly like ideal ones.

Question 6

Why does a capacitor act as an open circuit to DC voltage?

Accepted Answer

A capacitor acts as an open circuit to direct current because it blocks DC voltage once fully charged. However, it can get charged when initially connected to a battery. This property allows capacitors to block DC while letting alternating current pass, making them useful for AC coupling and filtering applications.

Question 7

What role does the electric field play in capacitor energy storage?

Accepted Answer

The energy stored in a capacitor is present in the electric field between its plates. By determining energy in terms of charge and capacitance, we quantify this field energy. Understanding this relationship is fundamental to analyzing capacitor behavior in circuits and designing systems like the design example automobile ignition system.

电容器中存储的能量