Glossary
Branch Current (RC Circuits)
The flow of electric charge through a specific path or segment of an RC circuit.
Example:
When a capacitor is fully charged in a DC circuit, the branch current through the capacitor becomes zero.
Capacitors
Electronic components that 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 for illumination.
Charging a Capacitor
The process where a capacitor accumulates electric charge and stores energy when connected to a voltage source, with its voltage asymptotically approaching the source voltage.
Example:
When you plug in your phone, its battery begins charging a capacitor internally to smooth out power delivery.
Discharging a Capacitor
The process where a charged capacitor releases its stored energy through a resistive path, causing its voltage and charge to decrease exponentially over time.
Example:
After unplugging a device, a power indicator light might slowly fade as an internal capacitor is discharging a capacitor through an LED.
Electric Potential Energy (Capacitor)
The energy stored within a capacitor's electric field due to the separation of charges on its plates.
Example:
A defibrillator stores a large amount of electric potential energy in its capacitors, which is then rapidly discharged to restart a heart.
Equivalent Capacitance
A single capacitance value that represents the combined effect of multiple capacitors in a circuit, simplifying overall circuit analysis.
Example:
When designing a complex filter, engineers often calculate the equivalent capacitance of several combined capacitors to simplify the circuit diagram.
Parallel Capacitors
Capacitors connected across the same two points in a circuit, where the equivalent capacitance is simply the sum of individual capacitances.
Example:
To increase the total energy storage capacity in a power supply, multiple parallel capacitors are often used.
Potential Difference (Capacitor)
The voltage across the plates of a capacitor, representing the work required per unit charge to move a charge between the plates.
Example:
As a capacitor charges, its potential difference increases until it matches the voltage of the power source.
RC Circuits
Electrical circuits that combine resistors and capacitors, creating unique electrical behaviors often used for timing and filtering applications.
Example:
A car's intermittent windshield wiper system uses an RC circuit to control the delay between wipes.
Resistors
Electronic components that oppose the flow of electric current, converting electrical energy into heat.
Example:
The heating element in a toaster is essentially a large resistor that gets hot when current flows through it.
Series Capacitors
Capacitors connected end-to-end along a single path, where the reciprocal of the equivalent capacitance is the sum of the reciprocals of individual capacitances.
Example:
To achieve a very precise, small capacitance value, a circuit designer might connect several larger series capacitors.
Steady State (RC Circuits)
The condition in an RC circuit after a long time (much greater than the time constant) where the capacitor is fully charged or discharged, and currents and voltages no longer change significantly.
Example:
In a DC RC circuit, once the steady state is reached, the capacitor acts like an open circuit, blocking any further DC current flow through its branch.
Time Constant (τ)
A characteristic time that determines how quickly a capacitor charges or discharges in an RC circuit, calculated as the product of the equivalent resistance and capacitance (τ = RC).
Example:
If a circuit has a large time constant, it will take a long time for the capacitor to fully charge, like a slow-filling water tank.