Glossary
Capacitor
An electrical component designed to store electrical energy in an electric field between two conductive plates separated by a dielectric material.
Example:
A camera flash uses a capacitor to quickly release a burst of stored energy to power the light.
Capacitors in Parallel
A circuit configuration where multiple capacitors are connected across the same two points, resulting in the same voltage across each. Their total capacitance is the sum of individual capacitances.
Example:
Connecting multiple small capacitors in parallel can create a large energy reservoir for a power supply, allowing it to handle sudden demands.
Capacitors in Series
A circuit configuration where capacitors are connected end-to-end, sharing the same charge but dividing the total voltage across them. Their equivalent capacitance is found using the reciprocal sum formula.
Example:
In high-voltage applications, capacitors in series are often used to distribute the voltage stress across multiple components, preventing breakdown of a single capacitor.
Charging a Capacitor
The process by which a capacitor accumulates electric charge when connected to a voltage source, causing its voltage to increase exponentially over time.
Example:
When you plug in a device, its power supply begins charging a capacitor to smooth out the incoming voltage.
DC Circuit
An electrical circuit where current flows in only one direction, typically powered by a constant voltage source like a battery.
Example:
A flashlight powered by batteries is a simple DC circuit.
Discharging a Capacitor
The process by which a charged capacitor releases its stored electric charge, typically through a resistor, causing its voltage to decrease exponentially over time.
Example:
When a camera flash fires, the capacitor is rapidly discharging a capacitor through the xenon lamp.
Open Switch (Capacitor Behavior)
The behavior of a fully charged capacitor in a DC circuit at steady state, where it effectively blocks the flow of direct current, acting as if there is a break in the circuit.
Example:
At steady state, the capacitor in a DC circuit behaves like an open switch, preventing current from flowing through its branch.
RC Circuit
An electrical circuit composed of at least one resistor and one capacitor, which exhibits time-dependent behavior during charging or discharging.
Example:
A car's intermittent windshield wiper control often uses an RC circuit to set the delay time between wipes.
Steady State
The condition in a DC circuit after all transient effects have subsided, where currents and voltages have reached constant values. For a capacitor, this means it is fully charged and acts as an open circuit.
Example:
After a long time, an RC circuit reaches steady state, and the capacitor voltage equals the source voltage.
Time Constant (τ)
A characteristic time for an RC circuit, defined as the product of resistance (R) and capacitance (C). It represents the time for the capacitor's voltage or charge to reach approximately 63.2% of its final value during charging, or decay to 36.8% during discharging.
Example:
A large time constant in an RC circuit means the capacitor will take a longer time to fully charge or discharge.
Total Capacitance (Parallel Capacitors)
The equivalent capacitance of a parallel combination, calculated by directly adding the individual capacitances.
Example:
Two 10μF capacitors connected in parallel have a total capacitance of 20μF.
Total Capacitance (Series Capacitors)
The equivalent capacitance of a series combination, calculated by summing the reciprocals of individual capacitances and then taking the reciprocal of that sum.
Example:
Two 10μF capacitors connected in series have a total capacitance of 5μF.
Total Charge (Parallel Capacitors)
The sum of the individual charges stored on each capacitor when they are connected in a parallel configuration.
Example:
If three parallel capacitors store 2μC, 3μC, and 5μC respectively, their total charge is 10μC.
Total Charge (Series Capacitors)
The charge stored on each individual capacitor in a series configuration, which is equal to the total charge supplied by the source to the combination.
Example:
If a 12V battery charges two series capacitors, the total charge on the combination is the same as the charge on each individual capacitor.