Capacitors Definition

An electronic component which shows electrostatic energy in an electric field is known as a capacitor. It looks like a battery but has distinct working as a battery converts chemical energy into mechanical energy. Capacitor stores energy in the form of electric charge. This electrical device has two terminals known as conductors. Distance between the charges decreases the force between them, whereas charge values increase the force. Insulating material, known as a dielectric, is used to create the distance between these conductors. The potential to store charges in the capacitor is known as its Capacitance. There comes the point in the capacitor when it carries charges more than its potential or Capacitance with respect to voltage. This period of time is known as the charging time of the capacitor.

Working of the capacitor

1. Consider two plates parallel to each other with a dielectric between them to create the distance.
2. Connect a DC voltage source to the whole capacitor. Connect one plate to the positive end (let it be plate 1) and the other to the negative end (let it be plate 2).
3. Pass the capacity of the battery to the whole capacitor, and this will turn plate 1 to positive as plate 2.
4. The electric current passed flows from the positive plate to the negative plate. Current does not flow when there exists an insulation material between them.
5. The positive end, i.e., plate 1, accumulates the positive charges, and the negative end, i.e., plate 2, accumulates negative charges across the capacitor.
6. Now remove the battery, and we will see the capacitor acting as the source of electrical energy by still holding negative and positive charges at its negative and positive ends or plates, respectively.

Determining the values of the capacitor

Charges (Q+ or Q-) on the conducting plates create the electric field between the plates. Also, potential difference and electric field are directly proportionate to each other. The capacitor is also referred to as the change in the ratio between the electric charge and the change in the electric potential. The Capacitance of a capacitor depends upon its usage. It can be fixed and variable as well. The Capacitance depends on the capacitor's shape and size and the insulator used between the conducting plates, i.e., positive and negative plates.

How is energy stored in the capacitor?

Charges are put in use by letting them flow towards each other in a circuit when opposite charges are placed parallel to each other in a capacitor.

U = ( CV )( CV ) / 2

Capacitors are like rechargeable batteries. There exist some differences between the working of capacitors and batteries, due to which they are different from each other. Capacitor does not gain energy from chemical reaction like batteries do.

Difference between the capacitor and battery

Both capacitors and batteries are made to deliver for the same motive but still carry some significant differences which are given below:

• The potential energy in the capacitor is stored in the electrical field, whereas, in the battery, it is stored as chemical energy, which later converts to mechanical energy.
• The battery is an active component of the circuit, and the capacitor is a passive component.
• Capacitor has lower energy density when compared to a battery.
• Since the capacitor stores energy directly on its conducting plate, therefore charging and discharging rates are faster. But in the case of the battery, energy is stored in the form of chemical energy, which later converts to mechanical energy, therefore leading to a comparatively slower rate of charging and discharging.
• The battery runs for a long time as compared to that of the capacitor.
• A capacitor is generally more expensive than a battery.
• Voltage in a capacitor decreases with its continued usage, but the voltage in a battery remains constant.
• Capacitor is made up of a thin sheet of metal and some insulating material, whereas metals and chemicals make up a battery.

Standard units of Capacitance

Farad is the standard unit of Capacitance but is relatively large for practical situations. Therefore, microfarads and picofarads are the subunits of farads to be used as measures.

• 1 millifarad = 10^-3 F
• 1 microfarad = 10^-6 F
• 1 nanofarad = 10^-9 F
• 1 picofarad = 10^-12 F

Different types of capacitors

Capacitors are available in different shapes and sizes. The most common capacitors are ceramic capacitors, super capacitors and electrolytic capacitors.

Ceramic capacitors- These capacitors carry relatively small charges and leak less current. They are also the cheapest capacitors. These capacitors are easily identifiable by the small bulbs, either in red or yellow colour.

Electrolytic capacitors- These capacitors look the same as the small tin cans on a circuit board. However, they are small in size but carry a good amount of charge and leak current very easily and quickly when compared to that ceramic ones. These capacitors perform their function when they are wired in a specific orientation. The positive pin on the capacitor is known as the anode, and the negative pin is known as the cathode. The positive side, i.e., the anode, is connected to the side to get a higher voltage. As they easily discharge current, that is why they are not considered the best option to store energy.

Super capacitors- These are used to store a good amount of energy. They can hold more voltage. These capacitors can discharge all their charges easily.

How to choose the best capacitor?

Keep in mind the following attributes by choosing the capacitors :

1. Size- Size does not only refer to its physical size, but also its potential to hold the charge, i.e., its capacitance. So choose the capacitor according to the capacitance you require.
2. Maximum voltage- Each capacitor has a limit to which it can carry the largest amount of voltage. Therefore, you have to choose the capacitor seeing its maximum voltage. As told earlier, different capacitors have different voltages; capacitors can vary from 1.5 V to 100 V.
3. Tolerance- Like resistors, capacitors, too, have variable tolerance, which varies from -1 % to -20% or 1% to 20% of the mentioned value.
4. Equivalent series resistance- Sometimes, capacitor's terminals have the potential of carrying a very small amount of resistance which sometimes becomes an issue when mindful of heat is required. Therefore, this factor needs to be considered while choosing the capacitor.
5. Leakage current- As mentioned earlier, it's the nature of discharging stored charges; unlike the batteries, it is an important variable to keep in mind the extent or amount of its leakage.