Glossary
Circuit Analysis
The process of determining the currents, voltages, and power dissipations in various parts of an electrical circuit, often using principles like Ohm's Law and Kirchhoff's Rules.
Example:
Using Kirchhoff's rules to find the current flowing through each resistor in a complex network is an example of circuit analysis.
Conservation of Energy
A fundamental physical principle stating that energy cannot be created or destroyed, only transformed from one form to another. Kirchhoff's Loop Rule is a direct consequence of this principle in circuits.
Example:
In a circuit, the chemical energy stored in a battery is transformed into electrical energy, which is then dissipated as heat and light in resistors, demonstrating the conservation of energy.
Electric Potential
A scalar quantity representing the amount of electric potential energy per unit charge at a given point in an electric field. It is often referred to as voltage.
Example:
A 9V battery creates an electric potential difference of 9 volts between its terminals, driving charges through a circuit.
Electric Potential Energy
The energy a charge possesses due to its position in an electric field. Changes in this energy occur as charges move through circuit elements.
Example:
As an electron moves from the negative terminal to the positive terminal of a battery, its electric potential energy increases, similar to lifting an object against gravity.
Electric Potential Graphs
Visual representations that plot the electric potential at different positions around a circuit loop, illustrating potential increases across sources and drops across loads.
Example:
An electric potential graph for a simple series circuit would show a sharp rise at the battery, followed by gradual drops across each resistor, returning to the starting potential.
Kirchhoff's Junction Rule
A principle stating that the total current entering a junction (or node) in a circuit must equal the total current leaving that junction, reflecting the conservation of charge.
Example:
At a point where a main wire splits into two branches, Kirchhoff's Junction Rule dictates that the current in the main wire equals the sum of the currents in the two branches.
Kirchhoff's Loop Rule
A fundamental principle stating that the sum of all electric potential differences (voltages) around any closed loop in a circuit must equal zero, directly reflecting the conservation of energy.
Example:
When analyzing a series circuit with a battery and two resistors, applying Kirchhoff's Loop Rule means the voltage supplied by the battery equals the sum of the voltage drops across the two resistors.
Potential Difference (Voltage)
The change in electric potential between two points in a circuit, representing the work done per unit charge to move a charge between those points.
Example:
A resistor causes a potential difference (or voltage drop) across it, meaning the electric potential is lower after the current passes through it.
Sign Conventions
The established rules for assigning positive or negative signs to potential differences (voltage changes) when traversing circuit elements in a specific direction during loop analysis.
Example:
When applying the loop rule, if you traverse a resistor in the direction of current, the potential change is a negative voltage drop (e.g., -IR), following standard sign conventions.
Voltage Drops
Decreases in electric potential as current flows through passive circuit elements like resistors, where electrical energy is converted into other forms (e.g., heat).
Example:
When current flows through a light bulb, it experiences a voltage drop as electrical energy is converted into light and heat.
Voltage Rises
Increases in electric potential as current flows through active circuit elements like batteries or power sources, where chemical or other energy is converted into electrical energy.
Example:
Moving from the negative to the positive terminal of a battery results in a voltage rise, providing the energy to drive the circuit.