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Question

What is the working principle of a capacitor?


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Solution

Capacitor:

  1. A capacitor is a device that is used to store charges in an electrical circuit.
  2. A capacitor works on the principle that the capacitance of a conductor increases appreciably when an earthed conductor is brought near it.
  3. Hence, a capacitor has two plates separated by a distance having equal and opposite charges.
  4. The space between the conductors may be filled by vacuum or with an insulating material known as a dielectric. The ability of the capacitor to store charges is known as capacitance.
  5. Equation of capacitance is given by, q=CV[q=charge,C=capacitance,V=voltage]

Working principle of a capacitor:

  1. Consider the following circuit, which shows the working principle of a parallel plate capacitor with a dielectric between them.
  2. Apply the voltage V as shown in the circuit, with plate 1 being positive and plate 2 being negative. An electric field appears across the capacitor.
  3. When the voltage is supplied to these plates, plate 1 will carry a positive charge from the battery, and plate 2 will carry a negative charge from the battery.
  4. The voltage is supplied for a period of time, during which time the capacitor is charged to its maximum holding charge, and this period is referred to as the capacitor's charging time.
  5. After a period of time, when the capacitor has reached its full charging capacity, we will turn off the electricity to the capacitor. The two plates have a negative and positive charge for a period of time.
  6. As a result, the capacitor serves as a source of electricity. If these plates are connected to a load, current flows from plate 1 to plate 2 until all charges on both plates have been dissipated.
  7. The time it takes for the capacitor to discharge is referred to as the dissipation time.


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