High School Physics : Using Capacitor Equations

Study concepts, example questions & explanations for High School Physics

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Example Questions

Example Question #2 : Capacitors

Three capacitors in parallel have a capacity of \(\displaystyle 2F\)\(\displaystyle 12F\), and \(\displaystyle 8F\), respectively. What is the total capacitance?

Possible Answers:

\(\displaystyle 0.045F\)

\(\displaystyle 22F\)

\(\displaystyle 1.41F\)

\(\displaystyle 4.23F\)

\(\displaystyle 7.33F\)

Correct answer:

\(\displaystyle 22F\)

Explanation:

The formula for capacitors in parallel is:

\(\displaystyle C_{eq}=C_1+C_2+C_3...\)

Plug in our given values:

\(\displaystyle C_{eq}=2F+12F+8F\)

\(\displaystyle C_{eq}=22F\)

Example Question #4 : Capacitors

Three capacitors in series have a capacity of \(\displaystyle 2F\)\(\displaystyle 12F\), and \(\displaystyle 8F\), respectively. What is the total capacitance?

Possible Answers:

\(\displaystyle 0.71F\)

\(\displaystyle 7.33F\)

\(\displaystyle 0.45F\)

\(\displaystyle 22F\)

\(\displaystyle 1.41F\)

Correct answer:

\(\displaystyle 1.41F\)

Explanation:

The formula for capacitors in series is:

\(\displaystyle \frac{1}{C_{eq}}=\frac{1}{C_1}+\frac{1}{C_2}+\frac{1}{C_3}...\)

Plug in our given values:

\(\displaystyle \frac{1}{C_{eq}}=\frac{1}{2F}+\frac{1}{12F}+\frac{1}{8F}\)

\(\displaystyle \frac{1}{C_{eq}}=0.70833\frac{1}{F}\)

\(\displaystyle C_{eq}=1.41F\)

 

Example Question #1 : Using Capacitor Equations

Three capacitors of equal capacitance are in a series circuit. If the total capacitance is \(\displaystyle 12F\), what is the capacitance of each individual capacitor?

Possible Answers:

\(\displaystyle 36F\)

\(\displaystyle 4F\)

\(\displaystyle \frac{1}{4}F\)

\(\displaystyle \frac{1}{36}F\)

\(\displaystyle 3F\)

Correct answer:

\(\displaystyle 36F\)

Explanation:

The formula for capacitors in a series is:

\(\displaystyle \frac{1}{C_{eq}}=\frac{1}{C_1}+\frac{1}{C_2}+\frac{1}{C_3}...\)

Since we have three equal capacitors, we can say:

\(\displaystyle \frac{1}{C_{eq}}=\frac{1}{C}+\frac{1}{C}+\frac{1}{C}=3*\frac{1}{C}\)

Using the value for total capacitance, we can find the value for the individual capacitance.

\(\displaystyle \frac{1}{C_{eq}}=\frac{3}{C}\)

\(\displaystyle \frac{1}{12F}=\frac{3}{C}\)

\(\displaystyle 36F=C\)

Example Question #2 : Using Capacitor Equations

Three capacitors of equal capacitance are in a parallel circuit. If the total capacitance is \(\displaystyle 12F\), what is the capacitance of each individual capacitor?

Possible Answers:

\(\displaystyle 3F\)

\(\displaystyle 4F\)

\(\displaystyle \frac{1}{12}F\)

\(\displaystyle \frac{1}{36}F\)

\(\displaystyle 12F\)

Correct answer:

\(\displaystyle 4F\)

Explanation:

The formula for capacitors in parallel is:

\(\displaystyle C_{eq}=C_1+C_2+C_3...\)

Since we have three equal capacitors, we can say:

\(\displaystyle C_{eq}=C+C+C=3C\)

Use the value for total capacitance to find the individual capacitance value.

\(\displaystyle C_{eq}=3C\)

 \(\displaystyle 12F=3C\)

\(\displaystyle \frac{12F}{3}=C\)

\(\displaystyle 4F=C\)

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