Glossary
Capacitor Charging
The process by which an uncharged capacitor accumulates electric charge when connected to a voltage source, causing its voltage to increase and the circuit current to decrease exponentially.
Example:
When you plug in a new electronic device, its internal power supply undergoes capacitor charging to stabilize the voltage before it reaches other components.
Capacitor Discharging
The process by which a charged capacitor releases its stored energy through a resistor, causing its charge, voltage, and the circuit current to decrease exponentially over time.
Example:
A defibrillator uses rapid capacitor discharging to deliver a high-energy electrical shock to restart a patient's heart.
Charge Conservation (in series capacitors)
In a series connection, the magnitude of charge stored on each individual capacitor is identical to the total charge stored by the equivalent capacitance of the series combination.
Example:
If a 10 µC charge is supplied to a string of series capacitors, each individual capacitor will hold exactly 10 µC of charge due to charge conservation.
Electromotive Force (E)
The voltage provided by an energy source, such as a battery or generator, that drives current and establishes potential differences in a circuit.
Example:
A 12V car battery provides the electromotive force necessary to power the vehicle's electrical systems.
Equivalent Capacitance
A single capacitance that can replace a combination of capacitors in a circuit without altering the circuit's overall electrical behavior.
Example:
When analyzing a complex circuit, replacing multiple capacitors with their equivalent capacitance simplifies the calculation of total charge or voltage.
Kirchhoff's Loop Rule
A fundamental principle stating that the algebraic sum of the potential differences (voltages) around any closed loop in a circuit must equal zero.
Example:
Applying Kirchhoff's Loop Rule to an RC circuit allows physicists to derive the differential equation that describes how charge and current change over time.
Parallel Capacitors
Capacitors connected across the same two points in a circuit, ensuring they all experience the same voltage.
Example:
Connecting multiple capacitors in parallel capacitors effectively increases the total plate area, resulting in a larger equivalent capacitance capable of storing more charge at the same voltage.
RC Circuit
An electrical circuit composed of at least one resistor and one capacitor, often connected to a voltage source, exhibiting time-dependent behavior.
Example:
A camera's flash unit utilizes an RC circuit to store energy in a capacitor and then rapidly discharge it through a lamp to produce a bright flash.
Series Capacitors
Capacitors connected end-to-end along a single path, where they all store the same magnitude of charge.
Example:
If you connect a 2 µF and a 4 µF capacitor in series capacitors, their combined equivalent capacitance will be smaller than 2 µF, demonstrating the reciprocal sum rule.
Steady State (RC Circuit)
The condition reached in an RC circuit after a long time (typically several time constants) when the capacitor is either fully charged or fully discharged, and all currents and voltages become constant.
Example:
In steady state in a DC circuit, a fully charged capacitor acts like an open circuit, effectively blocking any further DC current flow through its branch.
Time Constant (τ)
A characteristic time that quantifies how quickly a capacitor charges or discharges in an RC circuit, calculated as the product of the equivalent resistance and equivalent capacitance (τ = RC).
Example:
If an RC circuit has a short time constant, the capacitor will reach its full charge or discharge significantly faster than a circuit with a long time constant.