Combination of Capacitors

How Capacitors are connected?

Capacitors combination can be made in many ways. The combination is connected to a battery to apply a potential difference (V) and charge the plates (Q). We can define the equivalent capacitance of the combination between two points to be

Two frequently used methods of combination are: Parallel combination and Series combination

Related Topics

• Capacitor, Types and Capacitance
• Energy Stored in a Capacitor

Parallel Combination of Capacitors

 When capacitors are connected in parallel, the potential difference V across each is the same and the charge on C₁, C₂ is different i.e., Q₁ and Q₂.

The total charge is Q given as:

Equivalent capacitance between a and b is:

C = C₁ + C₂

The charges on capacitors is given as:

• \(\begin{array}{l}Q1=\frac{{{C}_{1}}}{{{C}_{1}}+{{C}_{2}}}Q\end{array} \)
• \(\begin{array}{l}Q2=\frac{{{C}_{2}}}{{{C}_{1}}+{{C}_{2}}}Q\end{array} \)

In case of more than two capacitors, C = C₁ + C₂ + C₃ + C₄ + C₅ + …………

Series Combination of Capacitors

When capacitors are connected in series, the magnitude of charge Q on each capacitor is same. The potential difference across C₁ and C₂ is different i.e., V₁ and V₂.

Q = C₁ V₁ = C₂ V₂

The total potential difference across combination is:

V = V₁ + V₂

The ratio Q/V is called as the equivalent capacitance C between point a and b.

The equivalent capacitance C is given by:

The potential difference across C₁ and C₂ is V₁ and V₂ respectively, given as follows:

In case of more than two capacitors, the relation is:

Important Points:

• If N identical capacitors of capacitance C are connected in series, then effective capacitance = C/N
• If N identical capacitors of capacitance C are connected in parallel, then effective capacitance = CN

Watch These Videos for Reference

Parallel Combination of Capacitor

Capacitors in Series

Problems on Combination of Capacitors

Problem 1: Two capacitors of capacitance C₁ = 6 μ F and C₂ = 3 μ F are connected in series across a cell of emf 18 V. Calculate:

• The equivalent capacitance
• The potential difference across each capacitor
• The charge on each capacitor

Sol:

(a)

(b)

(c) Q₁ = Q₂ = C₁ V₁ = C₂ V₂ = CV

Charge on each capacitor = C_eq V = 2μF x 18 volts = 36μC

In the above problem, note that the smallest capacitor has the largest potential difference across it.

Example 2: Find the equivalent capacitance between points A and B capacitance of each capacitor is 2 μF.

Sol: In the system given, 1 and 3 are in parallel. 5 is connected between A and B. So, they can also be represented as follows.

1. As 1 and 3 are in parallel, their effective capacitance is 4μF
2. 4μF and 2μF are in series, their effective capacitance is 4/3μF
3. 4/3μF and 2 μF are in parallel, their effective capacitance is 10/3μF
4. 10/3μF and 2μF are in series, their effective capacitance is 5/4μF
5. 5/4μF and 2μF are in parallel, their effective capacitance is 13/4μF

Therefore the equivalent capacitance of the given system is 13/4μF.

Introduction to Capacitors and Combination of Capacitors

Capacitors – Video Lesson

Top 10 Important Questions of Electrostatic Potential and Capacitance