Glossary
Ammeters
An instrument used to measure the electric current flowing through a point in a circuit, always connected in series.
Example:
An electrician might use an ammeter to check the current draw of an appliance.
Batteries
A device that converts chemical energy into electrical energy, providing a potential difference (voltage) to drive current in a circuit.
Example:
A car battery provides the initial electrical energy to start the engine.
Capacitance (C)
A measure of a capacitor's ability to store electric charge, defined as the ratio of the charge stored to the potential difference across its plates, measured in Farads (F).
Example:
A large capacitance value means a capacitor can store a significant amount of charge at a given voltage.
Capacitors
An electrical component designed to store electrical energy in an electric field, consisting of two conductive plates separated by a dielectric.
Example:
A camera flash uses a capacitor to quickly release a burst of stored energy to power the light.
Capacitors in Parallel
A configuration where capacitors are connected across the same two points, resulting in a total capacitance that is the sum of the individual capacitances.
Example:
Connecting two 10 μF capacitors in parallel results in an equivalent capacitance of 20 μF.
Capacitors in Series
A configuration where capacitors are connected end-to-end, resulting in a total capacitance that is less than the smallest individual capacitance.
Example:
Connecting two 10 μF capacitors in series results in an equivalent capacitance of 5 μF.
Charging Equation (Q(t))
A mathematical expression describing the exponential increase in charge on a capacitor over time during the charging process in an RC circuit.
Example:
Using the charging equation, you can predict how much charge will be on a capacitor after a specific time interval.
Charging a Capacitor
The process by which a capacitor accumulates electric charge when connected to a voltage source through a resistor.
Example:
When you plug in a device, its internal capacitors begin charging a capacitor, drawing current until they reach their full voltage.
Circuit Schematics
A simplified, standardized diagram that uses symbols to represent the components and connections within an electrical circuit.
Example:
Before building an electronic device, engineers first draw a detailed circuit schematic to plan the connections.
Closed Circuits
An electrical circuit where the path for current is complete and unbroken, allowing charge to flow.
Example:
When you press the button on a remote control, you complete a closed circuit that sends a signal.
Closed Loops
A complete, unbroken path that allows electric charge to flow continuously.
Example:
For a flashlight to turn on, its circuit must be a closed loop so electrons can travel from the battery, through the bulb, and back to the battery.
Conventional Current
The direction of electric current defined as the direction in which positive charge would flow, from higher potential to lower potential.
Example:
Even though electrons actually flow from negative to positive, conventional current is depicted as flowing from the positive terminal of a battery to the negative.
Discharging Equation (Q(t))
A mathematical expression describing the exponential decrease in charge on a capacitor over time during the discharging process in an RC circuit.
Example:
The discharging equation helps engineers design circuits where a capacitor needs to release its energy at a controlled rate.
Discharging a Capacitor
The process by which a charged capacitor releases its stored electric charge through a resistor, causing current to flow in the opposite direction.
Example:
After turning off a camera flash, the capacitor slowly begins discharging a capacitor through internal resistance.
Energy Stored in a Capacitor (U)
The potential energy stored in the electric field between the plates of a charged capacitor.
Example:
A defibrillator uses the energy stored in a capacitor to deliver a powerful electrical shock to a patient's heart.
Equivalent Resistance (Parallel)
The single resistance value that could replace all resistors in a parallel combination without changing the total current or voltage in the circuit.
Example:
Two 10 Ω resistors connected in parallel have an equivalent resistance of 5 Ω.
Equivalent Resistance (Series)
The single resistance value that could replace all resistors in a series combination without changing the total current or voltage in the circuit.
Example:
If you connect a 5 Ω and a 10 Ω resistor in series, their equivalent resistance is 15 Ω.
Farad (F)
The SI unit of capacitance, defined as one coulomb per volt (1 F = 1 C/V).
Example:
A typical capacitor in an electronic circuit might have a capacitance of a few microfarads.
Lightbulbs
An electrical component that produces light when electric current passes through its filament, acting as a type of resistor.
Example:
An old incandescent lightbulb glows brightly because its filament heats up due to electrical resistance.
Multiple Loops
A characteristic of complex circuits where current can follow more than one distinct closed path, and components may be shared between these paths.
Example:
In a complex house wiring system, a single junction box might be part of multiple loops supplying power to different rooms.
Ohm's Law
A fundamental law in electricity stating that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) between them (V=IR).
Example:
If you know the voltage of a battery and the resistance of a lightbulb, you can use Ohm's Law to calculate the current flowing through the bulb.
Open Circuits
An electrical circuit where the path for current is incomplete or broken, preventing charge from flowing.
Example:
If a wire breaks in a string of holiday lights, it creates an open circuit, causing all the lights to go out.
Parallel Circuit (Resistors)
A circuit configuration where components are connected across the same two points, providing multiple paths for current flow.
Example:
Most household electrical outlets are wired in a parallel circuit, allowing each appliance to receive the full voltage independently.
RC Circuit
An electrical circuit composed of at least one resistor and one capacitor, often used for timing or filtering applications.
Example:
The blinking lights on a bicycle often use an RC circuit to control the flash rate.
Resistors
An electrical component that opposes the flow of electric current, converting electrical energy into heat or light.
Example:
The heating element in a toaster is a type of resistor that gets hot when current flows through it.
Series Circuit (Resistors)
A circuit configuration where components are connected end-to-end, forming a single path for current flow.
Example:
Old Christmas lights where if one bulb burns out, the entire string goes dark, are wired in a series circuit.
Short Circuits
An unintended low-resistance path created in an electrical circuit, allowing current to bypass the intended load and often leading to excessive current flow.
Example:
If a frayed wire touches another conductor, it can create a short circuit, potentially causing sparks or overheating.
Standard Symbols
Universally recognized graphical representations used in circuit schematics to denote specific electrical components.
Example:
The zig-zag line is a standard symbol for a resistor in a circuit diagram.
Switches
A device used to interrupt or complete an electrical circuit, thereby controlling the flow of current.
Example:
Flipping a light switch opens or closes the circuit, turning the light on or off.
Time Constant (τ)
A characteristic time for an RC circuit, equal to the product of resistance and capacitance (τ = RC), representing the time for a capacitor to charge to 63.2% or discharge to 36.8% of its initial value.
Example:
If an RC circuit has a small time constant, the capacitor will charge or discharge very quickly.
Variable Elements
Electrical components whose value (e.g., resistance, capacitance) can be intentionally changed or adjusted.
Example:
A dimmer switch for lights uses a variable element (like a variable resistor) to control brightness.
Voltmeters
An instrument used to measure the electric potential difference (voltage) between two points in a circuit, always connected in parallel.
Example:
To check the voltage of a car battery, you would use a voltmeter across its terminals.
Wires
Conductive materials, typically metal, that provide a low-resistance path for electric current to flow.
Example:
The copper wires in your wall carry electricity to power your devices.