Math Problem Statement

Find net capacitance

Find the net capacitance of a circuit with C1 = 3.00 μF, C2 = 4.00 μF, and C3 = 2.00 μF connected to a voltage source of 21.0 V.

Solution

The given circuit contains three capacitors C1=3.00μFC_1 = 3.00 \, \mu F, C2=4.00μFC_2 = 4.00 \, \mu F, and C3=2.00μFC_3 = 2.00 \, \mu F, and a voltage source of V=21.0VV = 21.0 \, V. The capacitors C1C_1 and C2C_2 are connected in series, and this series combination is connected in parallel with C3C_3.

Steps to find the net capacitance:

  1. Capacitors in Series: For capacitors in series, the reciprocal of the equivalent capacitance C12C_{12} is given by: 1C12=1C1+1C2\frac{1}{C_{12}} = \frac{1}{C_1} + \frac{1}{C_2} Substituting the values: 1C12=13.00+14.00(μF1)\frac{1}{C_{12}} = \frac{1}{3.00} + \frac{1}{4.00} \, (\mu F^{-1}) Simplifying: 1C12=412+312=712\frac{1}{C_{12}} = \frac{4}{12} + \frac{3}{12} = \frac{7}{12} Therefore: C12=1271.71μFC_{12} = \frac{12}{7} \approx 1.71 \, \mu F

  2. Capacitors in Parallel: The equivalent capacitance of capacitors in parallel is simply the sum of their capacitances. So, the total capacitance CeqC_{eq} of C12C_{12} in parallel with C3C_3 is: Ceq=C12+C3C_{eq} = C_{12} + C_3 Substituting the values: Ceq=1.71+2.00=3.71μFC_{eq} = 1.71 + 2.00 = 3.71 \, \mu F

Thus, the net capacitance of the circuit is Ceq=3.71μFC_{eq} = 3.71 \, \mu F.

Would you like more details on any part of this solution or have further questions?

Follow-up Questions:

  1. What would happen if all three capacitors were connected in series?
  2. How does the voltage distribute across C1C_1 and C2C_2 in this configuration?
  3. How do you calculate the total energy stored in the circuit?
  4. What is the charge on each capacitor if the total voltage is 21.0 V?
  5. How would changing C3C_3 affect the overall capacitance?

Tip: For capacitors in series, the equivalent capacitance is always smaller than the smallest individual capacitor.

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Math Problem Analysis

Mathematical Concepts

Capacitance
Series and Parallel Capacitors

Formulas

For series capacitors: 1/Ceq = 1/C1 + 1/C2
For parallel capacitors: Ceq = C1 + C2

Theorems

Capacitor Combination Rules

Suitable Grade Level

Grades 10-12