Library / Foundations: Physics / FPH-24
Foundations: Physics
Capacitance
Charge stored per volt.
- Ref
- FPH-24
- Rev
- v1
- Field
- Foundations: Physics
- Result
- C [µF]
Capacitance in farads is charge per volt. Stored energy U = ½CV².
A capacitor with more capacitance holds more charge at the same voltage.
Calculator
µF
µC
V
- Stored energy ½CV²0.72 mJ
- Charge in mAh3.333×10−5 mAh
What drives the result
Each variable is moved across its typical range while the others stay at the values above. The longest bar is the key driver.
Capacitance (µF) current value 10 µF
QChargeKey driver
0.0833833
VVoltage
0.3120
- 1 µC per volt equals 1 µF; the units scale together.
- Capacitors store much less energy than batteries but can release it very quickly.
Chart data as tables
Ranked variables
| Variable | Typical range | Lowest result | Highest result | Swing (µF) | Local step | Change in result |
|---|---|---|---|---|---|---|
| Q Charge | 1 to 10,000 µC | 0.08333 | 833.3 | 833.3 | +10% | +10 % |
| V Voltage | 1 to 400 V | 0.3 | 120 | 119.7 | +10% | −9.09 % |
Sweep of Voltage
| Voltage (V) | Capacitance (µF) |
|---|---|
| 1 | 120 |
| 2.115 | 56.74 |
| 4.472 | 26.83 |
| 9.457 | 12.69 |
| 20 | 6 |
| 42.29 | 2.837 |
| 89.44 | 1.342 |
| 189.1 | 0.6344 |
| 400 | 0.3 |
Sweep one variable
Capacitance (µF)Hover, touch, or use the arrow keys on the chart
Variables and how each one contributes
C
Capacitance
What the equation gives you. Everything else feeds it.
Q
Charge
Charge stored. Directly proportional.
V
Voltage
Voltage across the capacitor. Inversely proportional.
Worked example with the values above
- Charge 120 µC at 12 V.
- Divide: 120 / 12.
- C = 10 µF.
Assumptions and limits
- Ideal capacitor with constant C.
- Charge on one plate (equal and opposite on the other).
Common mistakes
- Mixing µC with C.
- Using the supply voltage when the capacitor is not fully charged.
Statistics and uncertainty
Electrolytic capacitor tolerances of ±20% mean measured capacitance rarely matches the rating exactly.
Where it is used
- Power smoothing and pulse supplies.
- Timing circuits.
Maths you need
- Charge: coulombs
- Voltage: volts