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Introduction to Capacitor, Capacitance and its types

Capacitor

“A capacitor formerly known as condenser is a device used for storing electric charge energy electrostatically in an electric field.”

Capacitors
Capacitor

The forms of practical capacitors vary widely, but all contain at least two electrical conductors (plates) separated by a dielectric (insulator). The conductors can be thin films of metal, aluminum foil or disks, etc. The ‘nonconducting’ dielectric acts to increase the capacitor’s charge capacity. A dielectric can be glass, ceramic, plastic film, air, paper, mica, etc. It can be said that “a pair of conductors separated by a dielectric or insulator forms a capacitor.”

How Capacitor Works?

When we apply a potential difference or voltage across these two conductors, then a static electric field is formed across the insulator or dielectric, causing positive charge (+Q) to collect on one plate and negative charge (-Q) to collect on the other plate. Hence, positive charges are stored on one plate or conductor and negative charges on the other. Adding electrical energy to a capacitor is called charging; releasing the energy from a capacitor is known as discharging.
You can charge a capacitor simply by wiring it up into an electric circuit. When you turn on the power, an electric charge gradually builds up on the plates. One plate gains a positive charge and the other plate gains an equal and opposite (negative) charge. If you disconnect the power, the capacitors keeps hold of its charge (though it may slowly leak away over time). But if you connect the capacitors to a second circuit containing something like an electric motor or a flash bulb, charge will flow from the capacitor through the motor or lamp until there’s none remaining on the plates.

Capacitance

“Capacitance is the ability of a component or circuit to collect and store energy in the form of an electrical charge.”

The amount of electrical energy a capacitor can store depends on its capacitance.

There are three ways to increase the capacitance of a capacitor. 

  • Increase the area of the conductor plates by any means.
  • Narrow the separation between plates as much as possible.
  • Make the dielectric as good an insulator as possible.

The unit for measuring the size of a capacitor is farads (F). One farad is a huge amount of capacitance so typically it is measured in nanofarads or picofarads and is calculated as using relation:

C = Q/V

Where C is capacitance, Q is charge and V stands for voltage.

Capacitors In Parallel

Capacitor In Parallel

When we connect capacitors in parallel connection then all the capacitors get same applied voltage. Hence their capacitances add up.

Capacitors Equation for parallel combination

Capacitors In Series

Capacitor In Series

When we connect capacitors in series connection then the applied voltage across the capacitors decreases. The total voltage difference is calculated as sum of the inverse of their capacitances. Thus the total series capacitance must be smaller than any other capacitor in the network.

Capacitors Equation for series combination

Types Of Capacitor

There are several different types of capacitors. Each type has its own advantages and disadvantages can be used in different applications. While the list below gives some of the major types, not all can be listed and there are some less well used or less common types that can be seen. However it does include most of the major types.

  1. Ceramic capacitors
  2. Film capacitors
  3. Paper capacitors
  4. Double-layer capacitors
  5. Vacuum capacitors
  6. Electrolytic capacitors
  7. Air gap capacitors
  8. Glass capacitors
  9. Mica capacitors

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