What is Capacitor? What You Should Know!

What is Capacitor? What You Should Know!
what is capacitor

What is capacitor in electricity

A capacitor is one of the three fundamental electronic components, which are resistors, capacitors and inductors

Simple defination of the capacitor is: a capacitor is a device that stores electrical energy in an electric field

Capacitor in an electrical circuit

When we apply voltage across capacitor in an electrical circuit it behaves as a charge storage device

A capacitor is a passive two-terminal component which is used for the purpose of energy storage in an electric field.

What is capacitor construction

The very basic construction is two conductors or surfaces separated by dielectric medium isolation between them

Examples of dielectric media are air, glass, paper, ceramic or plastic

What does the voltage rating of capacitors mean?

The maximum voltage at which the capacitor can perform its duty perfectly is called its voltage rating. Above this voltage, the capacitor will malfunction and eventually destroy.

In other words, it is the threshold value above which that capacitor does not exist. The voltage rating of the capacitor ranges from -10V to 400V. Different capacitors have different voltage ratings. This is totally dependent on the user and what kind of capacitor he needs.

The user decides according to the potential difference at the point in circuitry. If one wants to use a capacitor in some circuitry where voltage is around 12 volts, a capacitor with a voltage rating of 24V must be used.

It is very convenient and guarantees you a life-long experience of no interruption in the system due to that capacitor. If you use 12 volts rated capacitor i.e., the working voltage of the capacitor = voltage rating of the capacitor. It’ll charge and discharge to 12V every now and then causing itself to meltdown or even burst up in some cases. The voltage rating of the Capacitor is an absolute value. It does not change.

Can I use a higher-rated capacitor?

Yes! One may use a higher-rated capacitor. The general rule of thumb to use a capacitor is to use the capacitor double the value actually needed. Use 13 volts rated capacitor in the place of the 6.3-volt point in the circuit.

If you want to replace your old capacitor with a new one while the new one has a higher voltage rating but not the double there is no problem. Say you are using a 130 Volts rated capacitor in a huge motor, and you want the capacitor to be replaced with a capacitor of 150 voltage rating. Then there is no problem in using the latter one.

But if the voltage in the machine is almost around 130 volts and you use the capacitor of 130 volts rating, it’ll go out of order in no time.

Some daily life problems may occur in this scenario. Like if the new capacitor, as it is a higher one in terms of voltage and capacitance, will be larger in size and may not fit in the same place as the old one did. Also, you have to replace the new capacitor in a way that the tolerance and capacitance do not change the function of the capacitor like adding a delay or making the system faster.

What is capacitor capacitance

Applying voltage f 1 volt across the capacitor stores charges in the capacitor, the amount of this charge is capacitance

So, the charge directly proportional to the voltage across the capacitor

While capacitance depends upon three main factors, active area of the capacitor, the distance between the conductors and the dielectric medium permittivity 

Differences between AC and DC capacitor?

The very basic difference between AC and DC capacitors is that the AC capacitors are non-polar capacitors, while DC capacitors are polar ones.

As the DC voltage does not change polarity, we may choose a polar or non-polar capacitor. When the voltage is applied the polar capacitor must have its positive terminal connected to the positive terminal of the battery and negative with the negative terminal.

Using a non-polar capacitor in DC is easier and more convenient because you just place the capacitor in a circuit without taking care of the terminals of the capacitor or the battery. In the case of AC supply, one must use the non-polar capacitor.

AC supply varies from positive to negative value several times within a second depending upon its frequency. If a polar capacitor is placed in the AC supply circuitry, this periodic interchange of values from positive to negative and vice versa melts down the capacitor.

While non-polar capacitor does not care about the polarity. If at an instance the positive current (conventional current) is flowing, it’ll conduct from positive to negative and vice versa.

What happens if you put a capacitor backward?

The answer depends upon the type of capacitor you are using. The response to this situation i.e., placing a capacitor backward is different for polar (polarized) or non-polar capacitors.

If the capacitor is non-polar then it does not matter which way you place it in the circuit. As there are no fixed terminals in sense of charge, non-polar capacitors remain totally unaffected by the connection they get on their ends. They do not change their capacitance and continue behaving normally.

If the capacitor is a polar capacitor, there may be some huge consequences of putting the capacitor in a backward connection.

  • Each polar capacitor has its polarity mentioned on it. The least effect of such irresponsibility while designing the circuit is that the capacitor does not work.
  • But if the capacitor, connected in reverse is connected in such a connection that provides a potential difference higher than the rated voltage, it’ll explode immediately.

These explosions could be of any scale ranging from a small fire in an automated system to a fire eruption and spreading in the whole facility you are working. This may lead to loss of material (infrastructures) to loss of lives.

How does a capacitor charge?

By wiring it up into an electric circuit. An electric charge gradually builds up on the plates when you turn on power.

Difference between capacitors and batteries?

Energy stored in a capacitor is in an electric field, while energy stored in a battery is in form of a chemical 

In general batteries provide higher energy storage capacity for longer time, while capacitors have rapid discharge and charge curve, So they can’t  replace batteries

 Which capacitor has the highest capacitance?

Out of all The best capacitor available is the Super Capacitors. The super capacitor is also known as the Ultra Capacitor, Double layered capacitors, and Electro-chemical capacitors.

At the expense of the voltage, Super Capacitor provides us with the best capacitance. The word best refers to the greater capacitance than the normal capacitors.

Generally, a conventional capacitor has two charged plates divided by a solid plate. But in the case of supercapacitors, the separator that separates the electrodes from each other is made of an ion-permeable material. This separator appears just like a divider between the electrodes.

The supercapacitor is filled with the electrolyte.  One of the best Supercapacitors is the Graphene Supercapacitor. Graphene is normally referred to as the “wonder material”. This wonder material is an atom-sized compound known for being the best conductor.

This best conducting property then reflects the capacitance of the capacitor. Graphene supercapacitors are so liked by the battery companies that they find it as the replacement for Lithium-ion batteries. Supercapacitors are eco-friendly.

They have strong mechanical strength and are also light absorbers. So, conclusively we can say that the Supercapacitor has the highest capacitance due to its unique structure and exclusive properties.

Which capacitor has the least variation?

The silver-plated Mica capacitor is the capacitor with the least variation. Mica is a naturally occurring silicate material.

Materials that have mica in them are normally shiny. So, when a shiny, and glazing capacitor is seen, you can say it is a mica capacitor. Mica can be readily divided into plates. Mica is a very stable mechanical and chemical mineral that is very convenient to be used as a capacitor base.

Chemical stability allows it to behave well even after a long time. The reason for the least variations is that the Mica capacitor is very non-reactive/stable when comes in contact with other materials.

Mica does not react with alkalis and bases, oils, or even with water. The aging of the capacitors is only possible due to these reactants found in the atmosphere that readily react with the capacitor. Mica being the non-reactive does not age.

It is a reliable, stable, and high-precision capacitor. So, if you want a capacitor that does not age and does not show variations in its output, a Silver-plated mica capacitor is the best choice.

What happens if you do not discharge the capacitor?

 A charged capacitor is a potential danger. It is a compromise to the safety of the systems around which you place it.

Charged capacitor hurts first, tells later. The biggest issue is that the capacitor will remain charged for a long unless it is discharged. And the problem is that there is no tester to actually find out the level of charge present in the capacitor.

So, conclusively, a charged capacitor especially the one with a higher capacitance should not be left around the electronic components for safety purposes.

Capacitor and electrical motors

Capacitors plays a very important role in single phase electrical motors running, as single phase motors need capacitor for starting its running “running capacitor”, While in three phase motors no need for starting capacitor. The capacitor makes a phase shift between the phase and the neutral. By this way the rotating filed affect the motor and makes its rotor to rotate.

With out this starting capacitor a single phase motor will hum and won’t start. To start the motor in this case you should give it a starting rotation by hand. Of course this is very dangerous solution, I recommend not to try it.

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