Introduction: The CAPACITOR

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Capacitor is a basic component in electronics.....
Mostly, every circuit in electronics field comprises at least a single capacitor. You can also find them in the circuits lying around you...

It's basically a component which provides Capacitance between two terminals in a circuit. It stores energy in it in the form of electric charge. It can charged and discharged many times in a circuit.Also, there are various values of capacitors available in the market for different applications.

Capacitors are also used in series or parallel combination. Any value of capacitance can be created by using series or parallel combinations. As capacitor stores electric charge and generates a voltage across it, choosing a proper capacitor with proper specs is a must for any application.

This Instructable explains about the basics of a Capacitor.

You can also refer the above video for a short and a simple basic explanation about the capacitor or check it out here -

Step 1: Understanding the Capacitor...

A Capacitor is a two terminal device (generally) and can have polarity on its terminals. ( positive & negative terminals )
A Capacitor has its capacitance value printed on it. On some capacitor (such as electrolytic) the capacitance value is given in Micro-Farads whereas on some capacitor (such as ceramic or polyester) the capacitance value is given in Pico-Farads.

The Common types of Capacitors available in the market are -

• Electrolytic Capacitors

• Ceramic Capacitors

• Polyester Capacitors

• Film Capacitors

• Tantalum Capacitors

• Variable Capacitors

and many more.....

The Capacitors are available in various voltage ratings too. These Voltage ratings depend on the use of capacitor in a specific application. The voltage rating is determined by the maximum value of the voltage that is to be applied to it. We'll will discuss about it more in the further steps.

Step 2: Calculation Parameters

There are various parameters which are considered which calculating the capacitance of a capacitor. They are as follows:

1) Charge stored in a Capacitor :

- It is calculated as Q = C x V

- Charge (Q - coulombs) on a capacitor's plates is the product of the capacitance (C - Farads) and the voltage (V - volts) across the device.

2) Energy stored in a Capacitor:

- It is calculated as W = 0.5 x (C x (V^2))

- Energy (W - Joules) stored in a capacitor is half the product of the capacitance (C - Farads) and the voltage (V - volts) across the device.

3) Capacitive Reactance:

- It is calculated as Xc = 1/ ( j x ω x C)

- Capacitive reactance (Xc - Ω) is inversely proportional to the frequency (ω - radians/sec or f - Hz) and capacitance (C - Farads).

and many more...

But in general, the value of a capacitance is totally dependent on its use in the application.

For eg:- Consider a Audio Amplifier Circuit running on a 12V rectified power supply.

Here, the rectifier circuit uses a 1000uF capacitor (16V) in order to smooth the output of the rectifier and get a constant and stable output. Also, a 0.1uF (16V) capacitor is used at the input terminals of the amplifier to block DC components of an input signal and to get a pure AC signal at the input.

Note - the capacitor voltage rating used in any circuit should be always greater than the maximum voltage in the circuit.

Step 3: Reading a Capacitor

Generally, the capacitance value of a capacitor is printed on its body. The value is stated in different ways for different capacitor. Some of them are as follows:

1) For Reading the value of an Electrolytic Capacitor :

- The Voltage rating and the capacitance value is directly mentioned on such capacitors. The unit is generally in Micro-Farads and Voltage Rating is in Volts. The SMD package of electrolytic capacitors have the same markings on them.

- They show presence of '-' signs on the body which indicates the Negative terminal of the Capacitor besides it.

2) For Reading the value of a Ceramic Capacitor :

- For normal ceramic capacitors, the value of capacitance is given in the form of a code. It is more similar to reading the value of a SMD resistor. The code mentioned in it, are of three digits.

For eg. - A ceramic Capacitor has 104 code written on it.

- Here, the first two digits are the starting digits (significant digits) of the capacitance value. and the last digit shows the power of 10 (multiplier) to which it must be raised to get the proper value. Thus, we have the capacitance with code 104 as 10x10^(4) . The value is stated in Pico-Farads. The value of the given capacitor becomes 100000 pico-farads, i.e., 0.1 Micro-Farads. The SMD package of ceramic capacitors don't have any code or markings on them.

The Voltage Rating of such capacitors is generally 50V unless mentioned.

3) For Reading the value of a Polyester Capacitor :

- The Capacitance Value is stated on it in the form of code. It is read as same as the ceramic capacitor. Plus it has an Alphabet just next to the code. It gives the value of the tolerance of capacitance variations of the capacitor. Refer to the chart given above

- The Voltage ratings are directly mentioned on it.

4) For Reading the value of a Tantalum Capacitor :

- The Capacitance value is directly mentioned on it in Micro-Farads.

- The Voltage reading is also mention on it in Volts.

The SMD package of tantalum capacitors have code and voltage markings on them.

Next to the voltage Rating, there's one small '+' sign, which indicated the positive terminal of the capacitor that lies below the sign.

Step 4: Getting Any Value for Your Projects

Some projects require intermediate values of capacitance other than standard values. Don't Worry !!!

You can make any required value of Capacitance in a very easy way.

Connecting Capacitance in a series or parallel manner helps to create any required value of capacitance.

Connecting in parallel adds up all the capacitance values whereas, connecting them in series decreases the total value of capacitance.

Capacitors in Parallel -

When Capacitor are connected in parallel, then the effective capacitance is given by - > C = ( C1 + C2 + C3 +......)

For example -

We have three capacitors of the values - 10uF , 100uF and 20uF.

So if we connect them in parallel we get the effective Capacitance as -

C = 10 + 100 + 20

C = 130uF

This shows that the value of capacitance has increased.

Note - Here, as all the capacitors are in parallel, the voltage rating remains the same for all. All the capacitors to be connected in parallel should be of same voltage rating. If this is not the case then, the capacitor with the smallest voltage rating dominates and that rating is the max rating of the capacitors connected in parallel.

So, in this way you can make any required big value of Capacitance.

Capacitance in Series -

When Capacitors are connected in series, then the effective capacitance is given by - > C = 1 / [(1/C1) + (1/C2) + (1/C3) + .....]

For example -

We have three capacitors of the values - 100uF , 50uF and 20uF.

So if we connect them in series we get the effective capacitance as -

C = 1/[(1/100) + (1/50) + (1/20)]

C = 1/[( 0.01) + (0.02) + (0.05)]

C = 1/[0.08]

C = 12.5uF

This shows that the value of capacitance has decreased.

Note - Here, as all the capacitors are in series, the voltage rating add up. All the capacitors to be connected in series can be of any voltage rating. The total sum of voltage ratings of each capacitor denoted the maximum voltage rating of the capacitors in series

So, in this way you can make any required small value of capacitance.

Step 5: Using a Capacitor

Capacitor has many uses in Electronics.
Some of the basic uses have been described below.

1) To filter the output of a Rectified Supply (De-coupling) --

- A rectified supply has positive cycles in its output. These are known as ripples which create fluctuations in the output. Hence, a high value capacitor is used at the output of such a circuit in order to lower the ripples and to obtain a smooth output waveform.

2) To stabilize a DC signal -

- In order to remove variations or to overcome the fluctuations in the signal, capacitors are used in parallel with the output. They are also used to obtain a stabilized reading from a sensor whose output has less stability.

3) In delay generation circuits --

- The charging and discharging ability of the capacitor is used for producing delay in various circuits. Turn-On delay & Turn-Off delay are some of the delays generated using a capacitor .

4) In DC-DC converters --

- DC - DC converters make use of capacitors for filtering purposes.

5) In AC Filters --

- The Capacitors are a part of variety of filters used in AC filter circuits. These capacitors with some additional components form different filters such as Low Pass, High Pass, Band pass, etc., types of filters which are used for signal filtering and conditioning.

6) In Audio circuits (Coupling) --

- In audio amplifiers and other audio devices, capacitors are used for removing the DC components from a signal. As Capacitors only pass AC through them, we obtain a pure AC signal at its output.

7) In AC Motor Starters --

- For starting a single phase induction motor capacitors are used.

Step 6: Finishing It !!!

Well, that's all about the Capacitor...

The basics of Capacitor can be ended-up here.

You can also refer other instructables or the internet for more Info about Capacitors.

Thanks for checking out this Instructable.......!!!

Check out the other instructables too:

The Resistor -

The Diode -

The LED -

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