8TH GRADE · RESISTANCE AND OHM'S LAW
Conductor resistance and rheostat
Material, length, cross-section and current regulation.
The entire theory of the lesson is collected here; you can read it without an account. In interactive mode, the same theory appears as cards, followed by questions. with checking the answer and task, and progress is saved.
Basic Concepts
Conductor resistance
The resistance of a homogeneous conductor increases with length, decreases with cross-sectional area and depends on the material.
A long, thin wire has more resistance than a short, thick wire of the same material.
Resistivity
A characteristic of a material that relates the resistance of a conductor to its length and cross-sectional area.
Copper's low resistivity makes it suitable for wiring, while higher value alloys make it suitable for heaters.
Rheostat
A variable resistor that changes the length of the conductor included in the circuit and thereby regulates the current.
A slider and one edge of the winding are connected to the circuit; Before switching on, the highest resistance is often set.
Physical quantities
Resistivity
Characteristics of the electrical resistance of the material.
Unit: ohm meter ·
Conductor length
The length of a homogeneous conductor, which affects its resistance.
Unit: meter ·
Sectional area
The cross-sectional area of a homogeneous conductor.
Unit: square meter ·
Lesson formulas
Conductor resistance
Resistance is equal to resistivity multiplied by length and divided by cross-sectional area.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.