What is resistivity, and why is it considered a material property rather than a property of a specific sample?

Resistivity is a measure of how strongly a material opposes the flow of electric current. It is a material property because it depends only on the nature of the material itself, not on the dimensions (length or cross-sectional area) of the sample.

Write the equation used to calculate resistivity from experimental measurements.

ρ = RA/L, where R is resistance, A is cross-sectional area, and L is length.

Calculate the resistivity when resistance = 49.8 Ω, cross-sectional area = 2.0 × 10⁻⁷ m², length = 1.78 m.

Resistivity = 49.8 × 2.0 × 10⁻⁷ ÷ 1.78 = 5.60 × 10⁻⁶ Ω m.

OCR A-Level Physics A H556

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Energy, Power and Resistance

Resistivity and how it is measured

3 things to know
Papers 2 and 3

Overview

Recall questions on resistivity as a material property, R = ρL/A, its unit and calculations, and measuring the resistivity of a wire: instruments, cross-sectional area from diameter and repeated diameter readings.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Numbers

State the equation that relates the resistance of a conductor to its resistivity, length, and cross-sectional area.

Numbers

Calculate the cross-sectional area when diameter = 0.001 m.

Key term

In the equation R = ρL/A, what does each symbol represent?

Questions from this subtopic

Each one with the model answer underneath.

1
What is resistivity, and why is it considered a material property rather than a property of a specific sample?
Model answer
Resistivity is a measure of how strongly a material opposes the flow of electric current. It is a material property because it depends only on the nature of the material itself, not on the dimensions (length or cross-sectional area) of the sample.
2
State the equation that relates the resistance of a conductor to its resistivity, length, and cross-sectional area.
Model answer
R = ρL/A, where R is resistance, ρ is resistivity, L is length, and A is cross-sectional area.
3
In the equation R = ρL/A, what does each symbol represent?
Model answer
R is resistance (in ohms), ρ is resistivity (in ohm-metres), L is the length of the conductor, and A is its cross-sectional area.
4
What is the SI unit of resistivity?
Model answer
The ohm-metre (Ω m).
5
Write the equation used to calculate resistivity from experimental measurements.
Model answer
ρ = RA/L, where R is resistance, A is cross-sectional area, and L is length.
6
Calculate the resistivity when resistance = 49.8 Ω, cross-sectional area = 2.0 × 10⁻⁷ m², length = 1.78 m.
Model answer
Resistivity = 49.8 × 2.0 × 10⁻⁷ ÷ 1.78 = 5.60 × 10⁻⁶ Ω m.

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Resistivity and how it is measured

Overview

What you need to know

State the equation that relates the resistance of a conductor to its resistivity, length, and cross-sectional area.

Calculate the cross-sectional area when diameter = 0.001 m.

In the equation R = ρL/A, what does each symbol represent?

Questions from this subtopic

What is resistivity, and why is it considered a material property rather than a property of a specific sample?

State the equation that relates the resistance of a conductor to its resistivity, length, and cross-sectional area.

In the equation R = ρL/A, what does each symbol represent?

What is the SI unit of resistivity?

Write the equation used to calculate resistivity from experimental measurements.

Calculate the resistivity when resistance = 49.8 Ω, cross-sectional area = 2.0 × 10⁻⁷ m², length = 1.78 m.

Other ways to work this

What is inside Levo

The 3-step method, run for you

Cram a whole paper in one sitting

Blank Blitz makes facts automatic

Build It gets the exam shape right

Test It catches misconceptions

Brain Breaks between sessions

Every question in Energy, Power and Resistance, on a schedule.