Glossary
Conservation of Charge
A fundamental principle stating that the total electric charge within an isolated system remains constant; charge cannot be created or destroyed, only transferred.
Example:
When you rub a balloon on your hair, charge is transferred from your hair to the balloon, but the total amount of charge in the hair-balloon system remains the same.
Current (in parallel circuits)
In a parallel circuit, the total current supplied by the source is the sum of the currents flowing through each individual branch.
Example:
If one branch of a parallel circuit draws 1 amp and another draws 0.5 amps, the total current from the battery will be 1.5 amps.
Current (in series circuits)
In a series circuit, the electric current is the same at all points throughout the circuit, as there is only one path for charge to flow.
Example:
If 2 amps flow through the first resistor in a series circuit, then 2 amps of current will also flow through every other resistor in that circuit.
Current Conservation
The principle that the rate of charge transfer (current) is conserved at every junction in an electrical circuit, meaning no charge is lost or gained.
Example:
In a circuit where a wire splits into two, the sum of the current conservation in the two smaller wires will always equal the current in the original wire.
Equivalent Resistance
The single resistance value that could replace a combination of resistors (series, parallel, or mixed) in a circuit without changing the total current or voltage.
Example:
When solving a complex circuit, you often simplify sections by calculating their equivalent resistance to make calculations easier.
Kirchhoff's Junction Rule
A rule based on the conservation of charge, stating that the total electric current entering a junction (a point where wires connect) must equal the total current leaving that junction.
Example:
If 5 amps of current flow into a junction, and one branch carries 2 amps, then the other branch must carry 3 amps for Kirchhoff's Junction Rule to hold true.
Loop Rule
Also known as Kirchhoff's Voltage Law, it states that the sum of all voltage changes around any closed loop in a circuit must be zero, reflecting the conservation of energy.
Example:
Starting from the battery and going around a series circuit, the voltage gained from the battery minus the voltage drops across each resistor will sum to zero, illustrating the Loop Rule.
Parallel Circuits
An electrical circuit configuration where components are connected across the same two points, providing multiple paths for current to flow.
Example:
The electrical outlets in your house are wired in a parallel circuit, allowing each appliance to receive the full voltage independently.
Resistance (in parallel circuits)
In a parallel circuit, the reciprocal of the total resistance is the sum of the reciprocals of the individual resistances, resulting in a decrease in overall resistance.
Example:
Connecting two 10-ohm resistors in parallel results in a total resistance of 5 ohms, which is less than either individual resistor.
Resistance (in series circuits)
In a series circuit, the total resistance is the sum of the individual resistances of all components, leading to an increase in overall resistance.
Example:
Connecting a 10-ohm resistor and a 20-ohm resistor in series results in a total resistance of 30 ohms.
Series Circuits
An electrical circuit configuration where components are connected end-to-end, forming a single path for current to flow.
Example:
A string of old Christmas lights where if one bulb burns out, the entire string goes dark, is an example of a series circuit.
Voltage (in parallel circuits)
In a parallel circuit, the voltage drop across each branch is the same and equal to the voltage supplied by the source.
Example:
If a 12V battery powers a parallel circuit, every branch connected directly across the battery will experience a 12V voltage drop.
Voltage (in series circuits)
In a series circuit, the total voltage supplied by the source is divided among the components, with the sum of individual voltage drops equaling the source voltage.
Example:
If a 9V battery powers two resistors in series, and one resistor has a 4V drop, the other resistor must have a 5V voltage drop.