Lesson: Resistance and Resistivity of Conductors Physics • 9th Grade

In this lesson, we will learn how to relate the dimensions of and the motion of free electrons through an object to its resistance.

Lesson Plan

Students will be able to

use the formula to relate the resistivity, resistance, and dimensions of a resistor,
diagrammatically represent, in terms of the motion of free electrons, the effects of varying the length, cross-sectional area, and resistivity of a resistor on its resistance,
diagrammatically represent, in terms of the motion of free electrons, the effects of varying the temperature of resistors,
use the formula to relate the current in a resistor to the drift speed of free electrons in the resistor.

Lesson Presentation

Lesson Video

Lesson Explainer

Lesson Playlist

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Lesson Flashcards

Lesson Worksheet

Q1:

Which of the following formulas correctly relates the resistivity, , of a substance to the resistance of an object with a length, , that is made of the substance if the object has a cross-sectional area and a resistance ?

Q2:

A wire made of an unknown substance has a resistance of 125 mΩ. The wire has a length of 1.8 m and a cross-sectional area of m². What is the resistivity of the substance from which the wire is made? Give your answer in scientific notation to one decimal place.

Q3:

A copper wire with a resistance of 12.8 mΩ has a cross-sectional area of m². Find the length of the wire. Use Ω⋅m for the resistivity of copper. Give your answer to one decimal place.