Capacitor
A capacitor is a device that stores electrical energy or electric charge in an electrical field. It is a passive electronic component with two terminals.
Construction
It consists of two thin metal plates, parallel to each other separated by a very little distance. The medium in between the two plates is air or a sheet of some insulator. This medium is known as a dielectric. If a capacitor is linked to a battery of V volts, then the battery moves a charge +Q from plate B to plate A, so that -Q charge appears on plate A and +Q charge appears on plate B.
The charges on each plate draw in each other and thus stay bound within the plates. In this way, the charge is stored in a capacitor for a long period of time. Likewise, the charge Q stored on plates is directly proportional to the potential difference V throughout the plates i.e.,
Q ∝V
Q = CV
where C is the constant of proportionality, called the capacitance of the capacitor.
Capacitance
It is defined as the capability of the capacitor to store charge. It is provided by the ratio of charge and the electric potential as:
SI unit
SI unit of capacitance is the farad (F), defined as:
If one coulomb of charge given to the plates of a capacitor produces a potential difference of one volt in between the plates of the capacitor then its capacitance would be one farad.
Farad is a big unit, usually, we utilize a smaller-sized unit such as micro farad (μF), nano farad (nF) pico farad (pF), etc.
Combination of Capacitors
Capacitors are made with different standard capacitances, and by integrating them in series or in parallel, we can get any wanted value of the capacitance.
(i) Capacitors in Parallel
In this combination, the left plate of each capacitor is connected to the positive terminal of the battery by a conducting wire. In the same way, the right plate of each capacitor is connected to the negative terminal of the battery.
This kind of combination has the following attributes:
- Each capacitor linked to a battery of voltage V has the same potential difference V across it. i.e.,
V1 = V2 = V3 = V
- The charge developed across the plates of each capacitor will be different due to different values of capacitances.
- The total charge Q supplied by the battery is divided amongst the different capacitors. For this reason,
Q = Q1 + Q2 + Q3
Q = C1 V + C2 V + C3 V
C1 + C2 + C3
- Hence, we can change the parallel combination of capacitors with one equivalent capacitor having capacitance, such that.
Ceq =C1 + C2 + C3
When it comes to ‘n’ capacitors linked in parallel, the equivalent capacitance is given by
C eq =C1 + C2 + C3+… + Cn… 5. The equivalent capacitance of a parallel combination of capacitors is greater than any of the individual capacitances.
(ii) Capacitors in Series
In this combination, the capacitors are connected side by side i.e., the right plate of one capacitor is linked to the left plate of the next capacitor. This type of combination has the following attributes:
- Each capacitor has the same charge across it. If the battery supplies + Q charge to the left plate of the capacitor C1, due to induction– Q charge is induced on its right plate and +Q charge on the left plate of the capacitor C i.e.,
Q1 = Q2 = Q3 = Q
- The potential difference throughout each capacitor is different due to various values of capacitances.
- The voltage of the battery has been divided among the different capacitors. Thus,
V= V1 = V2= V3
- Thus, we can replace a series combination of capacitors with one equivalent capacitor having capacitance Ceq i.e.,
When it comes to ‘n’ capacitors connected in series, we have
MCQs:
- What is a capacitor?
- A. A device that generates electrical energy
- B. A device that stores electrical energy
- C. A device that converts electrical energy to mechanical energy
- D. A device that amplifies electrical signals
- Answer: B
- How are the plates of a capacitor arranged?
- A. They are perpendicular to each other
- B. They are circular in shape
- C. They are parallel to each other
- D. They are arranged randomly
- Answer: C
- What is the medium between the plates of a capacitor called?
- A. Conductor
- B. Insulator
- C. Semiconductor
- D. Superconductor
- Answer: B
- In the equation Q = CV, what does ‘C’ represent?
- A. Charge
- B. Voltage
- C. Capacitance
- D. Current
- Answer: C
- What is the SI unit of capacitance?
- A. Ohm
- B. Volt
- C. Farad
- D. Joule
- Answer: C
- Which unit is commonly used for smaller capacitance values?
- A. Millifarad
- B. Centifarad
- C. Microfarad
- D. Kilofarad
- Answer: C
- What is the equivalent capacitance of capacitors connected in parallel?
- A. Sum of their capacitances
- B. Product of their capacitances
- C. Reciprocal of their capacitances
- D. Ratio of their capacitances
- Answer: A
- In a parallel combination of capacitors, what is the potential difference across each capacitor?
- A. Different
- B. Zero
- C. Same
- D. Opposite
- Answer: C
- What happens to the total charge supplied by the battery in a parallel combination of capacitors?
- A. It remains the same
- B. It decreases
- C. It increases
- D. It becomes zero
- Answer: A
- How is the total capacitance of capacitors connected in series calculated?
- A. Sum of their capacitances
- B. Product of their capacitances
- C. Reciprocal of their capacitances
- D. Ratio of their capacitances
- Answer: C
- What is the equivalent capacitance of capacitors connected in series?
- A. Sum of their capacitances
- B. Product of their capacitances
- C. Reciprocal of their capacitances
- D. Ratio of their capacitances
- Answer: C
- In a series combination of capacitors, what is the charge across each capacitor?
- A. Different
- B. Zero
- C. Same
- D. Opposite
- Answer: C
- How is the voltage distributed in a series combination of capacitors?
- A. Equally
- B. Randomly
- C. Proportionally to their capacitances
- D. Inversely to their capacitances
- Answer: C
- What type of combination results in a higher equivalent capacitance?
- A. Parallel
- B. Series
- C. Both have the same equivalent capacitance
- D. It depends on the individual capacitances
- Answer: A
- What happens to the equivalent capacitance when capacitors are connected in parallel?
- A. It decreases
- B. It increases
- C. It remains the same
- D. It becomes zero
- Answer: B
- Which combination allows for obtaining any desired value of capacitance?
- A. Series
- B. Parallel
- C. Both
- D. Neither
- Answer: C
- What is the unit of capacitance for smaller values of capacitance?
- A. Millifarad
- B. Microfarad
- C. Nanofarad
- D. Picofarad
- Answer: D
- What is the dielectric medium between the plates of a capacitor?
- A. Metal
- B. Air
- C. Insulator
- D. Conductor
- Answer: C
- What does the charge stored on the plates of a capacitor depend on?
- A. Voltage
- B. Capacitance
- C. Both voltage and capacitance
- D. It does not depend on anything
- Answer: C
Summary:
Capacitors and Capacitance are fundamental concepts in electronics.
A capacitor is a device that stores electrical energy in an electrical field and consists of two parallel metal plates separated by a dielectric medium.
The capacitance of a capacitor is defined as its ability to store charge and is given by the ratio of charge to electric potential. The SI unit of capacitance is the farad (F), with smaller units such as microfarad (μF), nanofarad (nF), and picofarad (pF) commonly used.
Capacitors can be combined in series or parallel to achieve desired capacitance values.
In parallel combinations, each capacitor experiences the same potential difference, leading to a total charge distributed among the capacitors. The equivalent capacitance in parallel is the sum of individual capacitances.
In series combinations, each capacitor carries the same charge, but the potential difference across each capacitor varies. The equivalent capacitance in series is the reciprocal of the sum of reciprocals of individual capacitances.
Understanding these principles is crucial for designing electronic circuits and systems. Further exploration into the topic can lead to applications in various fields of electrical engineering and technology.