In this blog post, you will learn about capacitors, the 5 uses of capacitor, charging and discharging in a capacitor and much more. So, keep reading until the end of the blog post to get all the necessary information. Now let’s take a closer look at what a capacitor is.
Table of Contents
What is a Capacitor?
A capacitor is a two-terminal semiconductor device that is used to store electric charge. The capacitor is also called a condenser. The capacitor is also a passive component because it does not generate power. The capacitor is made by mixing dielectric material (insulator) between two conducting plates.
Capacitor Types and Symbols
The symbol of a capacitor depends on its type. There are two types of capacitors, fixed capacitors and variable capacitors.
Fixed Capacitor
In fixed capacitors, the value of the capacitor is fixed so that the plates cannot be adjusted. These capacitors prevent electric energy spikes from entering the electrical circuit, keeping the remaining components of the electrical circuit safe. These capacitors are used in timing circuits. There are two types of fixed capacitors, polarized and non-polarized.
Polarized capacitors
The polarized capacitor is a capacitor in which the positive (anode) and negative (cathode) terminals are fixed and never change. In this capacitor, the flow of current happens in a particular direction—polarized capacitors for example: electrolytic capacitors and super-capacitors.
Non-polarized capacitors
Non-polarized capacitors are those types of capacitors which do not have any polarity. No matter which way these capacitors are installed, they work well. These capacitors store very little electric charge. These capacitors are used in many types of electronic circuits such as noise filtering, audio coupling etc. Non-polarized capacitors for example ceramic, film, mica, glass, and polyester capacitors.
Variable Capacitor
A variable capacitor is a capacitor whose capacitance value can be adjusted to a certain range. Variable capacitor is made up of two metal plates and separated by an insulating plate. When the shaft of the variable capacitor is rotated the capacitance value changes. Variable capacitors for example trimmer capacitor, dielectric capacitor, piston capacitor.
MFD full form in Capacitor
MFD is the unit of capacitance of the capacitor. The full form of MFD is Micro Farad. MFD is a very small unit to check capacitance. Whenever any capacitor stores a charge, it is measured in farads. However, farad is a very large value, so we use microfarad or picofarad instead.
What are 5 uses of capacitor?
So, as you now know what a capacitor is, let us now understand what are the top 5 uses of capacitors.
- Energy storage
- Signal filtering
- AC to DC converter
- Remote sensing
- Power conditioning
Energy Storage
The ability of capacitors to store electric charge makes them ideal for a variety of applications, including flash lamps and UPSs (Uninterruptible Power Supplies) for storing power.
Signal filtering
Capacitors can also filter signals because they pass alternating current and block direct current. Additionally, capacitors block unwanted frequencies. They are used in many applications such as audio filtering, noise reduction, and radio reception.
AC to DC converter
The capacitor is also used to convert AC to DC. Capacitors are used in DC adapters where AC voltage is converted to DC voltage. A rectifier circuit is used to convert AC voltage to DC voltage. Applications such as laptop charger and mobile charger.
Remote sensing
Capacitors are also used for remote sensing. By using remote sensing, it is possible to detect, analyze, and measure proximity and humidity. It can sense different types of materials like skin, metal, plastic and liquid. Alternatively, remote sensing is called capacitive sensing. Applications such as touchscreen, metal detector etc.
Power conditioning
Capacitors are also used for power conditioning. Capacitors smooth out the fluctuations in voltage and current. Capacitors provide starting torque to electric motors and also improve the power factor.
How Capacitor Works
A capacitor is an electronic semiconductor device that stores electrical energy in the form of an electric field. The capacitor is made up of positive and negative conducting plates between which insulating material or vacuum is filled.
When the capacitor is connected to the battery then the electrons move from the negative terminal of the capacitor to the positive terminal and the potential difference created at both points, the electrons get stored on the dielectric material.
When the battery is disconnected from the circuit, the charge remains stored in the capacitor which can be used later. To calculate the capacitance of a capacitor, the charge stored (Q) is divided by the potential difference (V). C = Q/V
Charging and Discharging of Capacitor
Charging a capacitor means increasing the flow of electrons in the capacitor. To increase the flow of electrons inside the capacitor, the capacitor is connected to a power supply or a battery.
Discharging the capacitor means decreasing the flow of electrons inside the capacitor. To discharge the capacitor, the load must be connected to it.
Now let’s discuss in detail how capacitor charges and discharges.
How is the capacitor charged?
To charge the capacitor, the power supply is connected to the capacitor. When the capacitor is connected to the power supply, electrons flow inside the capacitor and an electric field is produced. Due to the production of the electric field, the charge is stored inside the dielectric material. Now, this charge stored can be used to supply power to the load.
How capacitor discharge?
A capacitor discharge occurs when the electric field inside the capacitor is exhausted and the potential difference between the conductive plates becomes zero. To discharge the capacitor, both the terminals of the capacitor have to be shorted or the capacitor has to be connected to a load.
How to Test a Capacitor in Circuit
There are 3 methods used to test the capacitor which are as follows:
Voltmeter method
To test the capacitor through a voltmeter, first of all, the voltage reading written on the capacitor is noted. This is the maximum voltage reading that the capacitor can tolerate, then the power supply is passed through the capacitor for a short time, then the supply is disconnected and the reading is noted. If the initial voltage reading is close to the final reading of the capacitor then the capacitor is correct.
Time Constant Method
To test the capacitor through time constant method, you must know the value of capacitance of the capacitor. In order to test the capacitor using the time constant method, you need to measure the time for charging the capacitor, which should be 63.2% of the applied voltage.
To test a capacitor using the time constant method, follow these steps:
- Use a stopwatch to calculate the time, once the voltage is applied on the capacitor such that the voltage drop reaches 63.2%, stop the stopwatch immediately after the applied voltage and note the time.
- Now calculate the time taken by putting it in the formula T = RC where T is the time constant, r is resistance, c is capacitance. If the product of time, resistance and capacitance is equal to or is close to then the capacitor is correct.
Multimeter Method
In order to check capacitors, digital multimeters are usually used because they are the easiest to use, and I am also one of them. Let us better understand how to check capacitors using a multimeter in great detail.
Electrolytic / Polarized capacitors
Electrolytic or polarized capacitors have greater ability to store charge. These capacitors are also used as temporary power banks. Follow these steps to check these capacitors with a multimeter:
- First of all set the digital multimeter to continuity mode (beep mode) .
- Connect the negative terminal of the capacitor with the negative (black wire) of the digital multimeter and connect the positive terminal of a capacitor with the positive (Red Wire) of multimeter.
- If you do this, the multimeter will show many readings and then display 1. This means that the capacitor is correct. If there is a beep sound on the multimeter or a continuous reading is shown on the multimeter display, it means that the capacitor is bad (you need to replace it).
Non-Electrolytic / Non-Polarised capacitors
Non-electrolytic or non-polarized capacitors are those capacitors in which the ability to store charge is very less. Mostly these capacitors are used for signal noise reduction or unwanted frequency cancellation. To check these capacitors with a digital multimeter, use the steps given below.
- First set the digital multimeter to continuity mode.
- Now connect both the terminals of the multimeter with any terminal of the capacitor because these capacitors do not have polarity.
- If the multimeter display does not show any reading instead of 1 then it means that the capacitor is fine. But if any reading is shown on the digital multimeter or a beep sound is made then it means that the capacitor is bad.
The Capacitor in AC circuits
Capacitors are commonly used in AC circuits. When an AC source is applied to the capacitor, the voltage across the plates of the capacitor increases and a charge begins to form. When a capacitor is charged, one side of its plate stores charge and the other side releases it.
How capacitor works in AC circuit
In AC circuits the capacitor charge increases as the AC voltage reaches its peak and the capacitor charge decreases as the AC voltage decreases. The capacitor is directly connected to the AC supply voltage. The capacitor is also used to improve the AC power factor.
Use of capacitor in AC circuit
Capacitors are used due to their special features in AC circuits.
- Capacitors provide starting torque to AC motors
- Signal filtering: Capacitors block low-frequency sound and pass high-frequency.
- Voltage variations: Capacitors store electrical energy in the form of an electric field and release it when required, thus eliminating the fluctuations in voltage.
- The capacitor is also used for power factor correction in AC circuits.
- Capacitors are also used in many AC circuits to store electric charge.
Conclusion
Capacitors are passive electronic components. The function of the capacitor is to store electric charge in the form of an electric field. Capacitors are mainly of two types: fixed capacitors and variable capacitors. The capacity to store the electric charge of fixed capacitors cannot be changed whereas the capacity to store the charge of variable capacitors can be increased or decreased.
Also Read:
Unlocking Diodes and their Applications
When transistors are used in digital circuits?
FAQ’s
How capacitor act as a filter?
Capacitors block DC and prevent noise from entering the circuit so that voltage fluctuations do not occur in the circuit. This is how capacitors act as filters in the circuit.
How do capacitors improve power factor?
When working with high inductive load applications, the current starts lagging and capacitors are used to compensate for this lagging current. Now as you know the current in the capacitor leads to the voltage, so by connecting the capacitors to the inductive load, the power factor will close to unity.
Does the capacitor work on DC or AC?
Yes, the capacitor works in both AC and DC. The capacitor does not store charge when used with an AC supply because the voltage in the AC keeps fluctuating. A capacitor stores the charge in DC voltage because the voltage in the DC supply remains instantaneous.
Polarized capacitors are more efficient in storing charge than non-polarized capacitors. This is because polarized capacitors are better suited for DC voltage. Non-polarized capacitors are more suitable for dealing with AC voltage fluctuations.
When does a capacitor act as a short circuit?
A capacitor acts like a short circuit when the capacitor is completely discharged and a sudden voltage is applied across it.
Why does the capacitor block DC?
The capacitor blocks DC because when DC voltage is applied on the capacitor then the capacitor starts storing the charge and as the charge in the capacitor becomes equal to the applied DC voltage then the voltage difference becomes zero at the terminals of the capacitor. This is the reason behind the capacitor blocking DC voltage