Glossary
Ammeter
An instrument used to measure the electric current flowing through a point in a circuit, always connected in series.
Example:
An electrician uses an ammeter to check if a circuit is drawing too much current, which could indicate a fault.
Battery
A power source that provides an electromotive force (EMF) to push electric charges through a circuit, maintaining a potential difference.
Example:
In a remote control, the battery supplies the energy needed for the infrared signal.
Capacitor
A passive two-terminal electrical component that stores electrical energy in an electric field between two conductive plates.
Example:
A capacitor in a camera flash stores charge and then rapidly releases it to produce a bright burst of light.
Charging a capacitor
The process by which a capacitor accumulates electric charge when connected to a voltage source through a resistor, with its charge and voltage increasing exponentially over time.
Example:
When you plug in a device, its internal power supply begins charging a capacitor to smooth out the incoming voltage.
Circuit schematics
Standardized diagrams that use symbols to represent electrical components and their connections, providing a universal language for circuit design and analysis.
Example:
Before building an electronic device, engineers first draw detailed circuit schematics to plan the layout and connections.
Closed circuit
A complete and unbroken path that allows electric current to flow continuously from the power source, through components, and back to the source.
Example:
For a toy car to move, its motor must be part of a closed circuit with the battery.
Conductive wires
Materials, typically metals, that provide low-resistance pathways for electric charge to move within a circuit.
Example:
Copper conductive wires are commonly used in household wiring due to their excellent electrical conductivity.
Conventional current
The direction in which positive charge would flow, defined as moving from the positive terminal to the negative terminal of a voltage source.
Example:
Although electrons flow the other way, circuit diagrams typically show conventional current flowing out of the positive terminal of a battery.
Discharging a capacitor
The process by which a charged capacitor releases its stored electric charge through a resistor, with its charge and voltage decreasing exponentially over time.
Example:
After unplugging a device, a discharging capacitor might keep an indicator light on for a few seconds as its stored energy dissipates.
Electric circuit
A closed loop that allows electric charges to flow continuously, enabling the transfer of electrical energy.
Example:
A flashlight is an electric circuit where a battery powers a bulb through a switch.
Energy stored in a capacitor
The potential energy stored in the electric field between the plates of a capacitor, given by the formula U = 1/2 CV^2.
Example:
The powerful flash on a camera uses the energy stored in a capacitor to produce a very bright, short burst of light.
Inductor
A passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it, resisting changes in current.
Example:
An inductor in an audio crossover network helps direct specific frequency ranges to the correct speaker drivers.
Kirchhoff's Current Law (Junction Rule)
States that the total electric current entering a junction (node) in a circuit must equal the total current leaving that junction, based on the conservation of charge.
Example:
At a circuit branch point, if 5 amps flow in and 2 amps flow out one path, then 3 amps must flow out the other path according to Kirchhoff's Current Law.
Kirchhoff's Voltage Law (Loop Rule)
States that the algebraic sum of the potential differences (voltages) around any closed loop in a circuit must be zero, based on the conservation of energy.
Example:
When tracing a path around a circuit loop, the voltage gains from batteries must exactly balance the voltage drops across resistors, as dictated by Kirchhoff's Voltage Law.
Lightbulb
An electrical component that converts electrical energy into light and heat, typically by heating a filament until it glows.
Example:
When you flip a switch, the lightbulb illuminates, demonstrating the conversion of electrical energy.
Open circuit
A circuit with a break or discontinuity in its path, preventing the flow of electric current.
Example:
If a wire breaks, it creates an open circuit, and the device connected to it will stop working.
Parallel connections
An arrangement where components are connected side-by-side across the same two points, meaning they all have the same potential difference across them.
Example:
Household outlets are wired in parallel connections so that each appliance receives the full line voltage independently.
RC circuit
An electrical circuit composed of at least one resistor and one capacitor, often used for timing or filtering applications.
Example:
A simple RC circuit can be used to create a delay in turning on an LED after a switch is closed.
Resistor
A passive two-terminal electrical component that limits or regulates the flow of electric current in a circuit.
Example:
A small resistor in an LED circuit prevents too much current from flowing and burning out the LED.
Series connections
An arrangement where components are connected end-to-end along a single path, meaning the same current flows through each component.
Example:
In old Christmas lights, if one bulb in a series connection burned out, the entire string would go dark because the circuit was broken.
Short circuit
An unintended low-resistance path in a circuit that allows a very large current to flow, often bypassing intended components and potentially causing damage or fire.
Example:
A frayed power cord can cause a short circuit, leading to sparks or tripping a breaker.
Switch
An electrical component used to open or close a circuit, thereby controlling the flow of electric current.
Example:
Flipping a switch on the wall completes the circuit, turning on the room lights.
Time constant (τ)
A characteristic time for an RC circuit, calculated as the product of resistance (R) and capacitance (C), representing the time it takes for a charging capacitor to reach approximately 63.2% of its maximum charge or for a discharging capacitor to fall to 36.8% of its initial charge.
Example:
If an RC circuit has a time constant (τ) of 1 second, it will take about 1 second for the capacitor to charge to 63% of its full capacity.
Voltmeter
An instrument used to measure the potential difference (voltage) between two points in a circuit, always connected in parallel.
Example:
A technician uses a voltmeter to ensure the correct voltage is supplied to a sensitive electronic component.