Example Data Table
| Case |
Known values |
Formula |
Expected result |
| Single capacitor |
Q = 120 uC, C = 47 uF |
V = Q / C |
2.553 V |
| Energy method |
E = 0.153 mJ, C = 47 uF |
V = sqrt(2E / C) |
2.552 V |
| Series bank |
10 uF, 22 uF, 47 uF at 12 V |
Vi = Q / Ci |
Largest drop on 10 uF |
| Parallel bank |
10 uF, 22 uF, 47 uF at 12 V |
Each Vi = Vs |
Each capacitor has 12 V |
Formula Used
For one capacitor, use V = Q / C. Here, V is potential difference, Q is charge in coulombs, and C is capacitance in farads.
Stored energy uses E = 1/2 C V2. Rearranged forms are V = sqrt(2E / C) and V = 2E / |Q|.
For series capacitors, use 1 / Ceq = 1 / C1 + 1 / C2 + ... . Then use Q = Ceq Vs and Vi = Q / Ci.
For parallel capacitors, use Ceq = C1 + C2 + ... . Every parallel capacitor has the same potential difference as the source.
How to Use This Calculator
Select the calculation method first. Enter the known charge, capacitance, energy, or source voltage. Choose the matching units beside each input.
For series or parallel banks, place capacitor values in the list box. Separate values with commas, spaces, semicolons, or new lines.
Enter a rated voltage and safety factor to check design margin. Press Calculate to view results above the form. Use CSV or PDF buttons for downloads.
Understanding Capacitor Voltage
Potential difference is the voltage across a capacitor. It shows how much electric pressure exists between its plates. A higher voltage means more stored charge for the same capacitance. Designers check it before choosing parts. The rated voltage must stay above the expected circuit voltage. This calculator helps you compare common capacitor relationships without changing pages.
Charge, Energy, And Capacitance
A capacitor stores charge when voltage is applied. The basic relation is simple. Voltage equals charge divided by capacitance. Energy gives another route. Stored energy equals one half times capacitance times voltage squared. These equations connect the same physical state. When any two values are known, the missing voltage can be found. Unit conversion is important. Microfarads, nanofarads, and picofarads differ by large powers of ten.
Series Capacitor Behavior
Series capacitors carry the same charge. Their voltages may be different. Smaller capacitance gets a larger voltage drop. This is why voltage balancing matters in high voltage banks. The equivalent capacitance is lower than any single series capacitor. After finding equivalent capacitance, the common charge is calculated from the supply voltage. Each capacitor voltage is then charge divided by its capacitance. The sum should match the source voltage, except for rounding.
Parallel Capacitor Behavior
Parallel capacitors share the same voltage. Their capacitances add directly. The total charge equals equivalent capacitance times applied voltage. Each branch charge depends on its own capacitance. Parallel groups are useful when larger storage is needed. They also reduce effective ripple in supply filters. The calculator reports branch charge and total stored energy for review.
Practical Design Checks
Capacitor voltage is not only a formula result. It is also a safety limit. Real capacitors have tolerance, leakage, temperature drift, and surge stress. Use a margin above calculated voltage. Many designs use a rating comfortably higher than normal operation. For pulsed circuits, check ripple current and dielectric type. For series stacks, add balancing resistors when leakage mismatch matters. Record assumptions with every result. Small notes prevent later design mistakes during troubleshooting. They also help teachers verify methods and units during grading. Clear records improve repeated calculations. Results from this tool support study, homework, prototyping, and review. Final hardware choices should follow datasheets and test conditions.
FAQs
What is potential difference in a capacitor?
It is the voltage between the two capacitor plates. It depends on stored charge and capacitance. The common formula is V = Q / C.
Why does a smaller series capacitor get more voltage?
Series capacitors have the same charge. Since V = Q / C, a smaller capacitance gives a larger voltage drop for that same charge.
Do parallel capacitors have different voltages?
No. Capacitors connected in parallel share the same two nodes. Each capacitor has the same potential difference as the source voltage.
Can I use microfarads directly?
Yes. Choose uF in the unit selector. The calculator converts microfarads to farads before applying the formulas.
What does the safety factor mean?
It multiplies the calculated peak voltage. This gives a design target above normal operation. A higher factor gives more voltage margin.
Does stored energy change the voltage formula?
It gives another way to find voltage. From E = 1/2 C V squared, the voltage is sqrt(2E / C).
Why is capacitor voltage rating important?
The rating is a limit set by the part design. Exceeding it can cause leakage, heating, dielectric breakdown, or failure.
Can this replace circuit testing?
No. It supports planning and learning. Real circuits need datasheet checks, tolerances, temperature review, and testing under expected conditions.