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Core Concepts
Understand the fundamental principles behind the calculations. These three concepts are the pillars of capacitor theory.
What is Capacitance?
Capacitance is the ability of a system to store an electric charge. Think of it as the 'capacity' of an object, like a capacitor, to hold charge. A higher capacitance means more charge can be stored for the same amount of voltage applied. The standard unit of capacitance is the Farad (F). Since a Farad is a very large unit, capacitance is often expressed in smaller units like microfarads (μF), nanofarads (nF), or picofarads (pF).
Interactive Visualization
See the relationship between charge, capacitance, and voltage in action. Adjust the sliders to see how changing one variable affects the others based on the formula Q = C × V.
Frequently Asked Questions
Have more questions? Here are some common queries about capacitors and their properties.
A capacitor stores energy in an electric field between two conductive plates separated by an insulator (dielectric). When a voltage is applied, positive charge builds up on one plate and negative charge on the other. The charges are held in place by their mutual attraction across the dielectric, creating the electric field where energy is stored.
Think of a bucket and water. Capacitance is like the size of the bucket—it's a fixed property that determines how much water it *can* hold. Charge is like the actual amount of water currently *in* the bucket. You can have a large bucket (high capacitance) with only a little water in it (low charge).
Ideally, yes. But in reality, all capacitors have some internal "leakage resistance" through their dielectric material. This causes the stored charge to slowly leak away over time. High-quality capacitors can hold a charge for a very long time (days, weeks, or even longer), while others may discharge more quickly.
Capacitor Charge Calculator Units and Plausibility Checks
A capacitor charge calculator applies Q = C × V, where V is the voltage across the two terminals and C is the effective capacitance at that operating condition. The output is stored charge, not charging time; time behavior also depends on source and path impedance.
- Normalize capacitance: convert the selected prefix correctly:
1 µF = 10⁻⁶ F,1 nF = 10⁻⁹ Fand1 pF = 10⁻¹² F. - Use terminal voltage: enter the differential voltage actually present on the capacitor, not an unrelated supply label; voltage polarity determines the sign of
Q. - Read the charge unit:
1 C = 1 A·s; for example,100 µF × 12 V = 1.2 mC. - Use effective C: include tolerance, temperature, frequency and DC-bias effects; if C came from a PCB capacitance calculation, include material and geometry variation.
- Cross-check the result: verify
C = Q ÷ Vand calculate stored energy separately withE = ½ × C × V²; do not infer a time constant from charge alone.
