Glossary
Capacitance
A measure of a component's ability to store electric charge and electrical energy in an electric field. It is measured in farads (F).
Example:
A camera flash uses a capacitor to quickly store and then release a burst of energy for illumination.
Conservation of Electric Charge
The principle stating that the total electric charge in an isolated system remains constant; charge cannot be created or destroyed, only transferred.
Example:
In a lightning strike, charge is transferred from the cloud to the ground, but the total conservation of electric charge in the Earth-atmosphere system remains constant.
Current
The rate of flow of electric charge past a point or through a cross-sectional area. It is measured in amperes (A).
Example:
The brightness of a light bulb is directly related to the amount of current flowing through its filament.
Electric Charge
A fundamental property of matter that causes it to experience a force when placed in an electromagnetic field. It can be positive or negative and is measured in Coulombs (C).
Example:
When you rub a balloon on your hair, the transfer of electric charge makes the balloon stick to a wall.
Kirchhoff's Current Law (KCL)
States that the total current entering a junction (or node) in an electrical circuit must equal the total current leaving that junction. This law is based on the conservation of electric charge.
Example:
At a circuit junction where a main wire splits into two branches, the current flowing into the junction will exactly divide between the two branches, demonstrating Kirchhoff's Current Law.
Kirchhoff's Voltage Law (KVL)
States that the algebraic sum of the voltages (potential differences) around any closed loop in a circuit must be zero. This law is based on the conservation of energy.
Example:
When tracing a path through a circuit, if you start at one point and return to it, the total voltage gains must equal the total voltage drops, illustrating Kirchhoff's Voltage Law.
Ohm's Law
A fundamental law stating that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance between them (V=IR).
Example:
If you double the voltage across a resistor, Ohm's Law predicts that the current through it will also double, assuming constant resistance.
Parallel Circuit
An electrical circuit configuration where components are connected across the same two points, providing multiple paths for the current to flow.
Example:
The electrical outlets in your home are wired in a parallel circuit, allowing each appliance to receive the full voltage independently.
Power
The rate at which electrical energy is transferred or dissipated in a circuit. It is measured in watts (W).
Example:
A high-wattage appliance, like a hairdryer, consumes a lot of power to operate.
Resistance
A measure of how much a material opposes the flow of electric current, converting electrical energy into heat. It is measured in ohms (Ω).
Example:
A toaster uses a high-resistance heating element to generate enough heat to toast bread.
Resistivity
An inherent material property that quantifies how strongly a given material opposes the flow of electric current. It is measured in ohm-meters (Ω⋅m) and depends on temperature.
Example:
Copper has a very low resistivity, making it an excellent material for electrical wires, while rubber has a very high resistivity, making it an insulator.
Series Circuit
An electrical circuit configuration where components are connected end-to-end along a single path, so the same current flows through each component.
Example:
Old Christmas lights where if one bulb burns out, the entire string goes dark, are an example of a series circuit.