Resistance and Resistivity

Resistance

Resistance

The measure of how difficult it is for a current to flow through an electrical component, mathematically defined as R = V/I, measured in ohms (Ω).

Resistivity

The intrinsic property of a material determining how much it resists the flow of electric current, measured in ohm metres (Ωm), calculated as p = RA/I.

Ohm's Law

States that the current through a conductor is directly proportional to the potential difference across it, applicable to ohmic conductors at constant temperature.

Experiment to Find Resistivity of a Metal

Clamp a wire to a ruler, measure its length, connect it in a circuit, record voltmeter and ammeter readings, calculate resistance using R=V/I, vary lengths, plot resistance against length, find resistivity by multiplying the gradient of the line of best fit by the cross-sectional area.

Resistance

The measure of how difficult it is for a current to flow through an electrical component, mathematically defined as R = V/I, measured in ohms (Ω).

Resistivity

The property of a material determining how much it resists the flow of electric current, defined as p = RA/I, measured in ohm metres (Ωm).

Ohm's Law

States that the current through an ohmic conductor is directly proportional to the potential difference across it (I ∝ V), applicable to conductors like metals.

Experiment to Find Resistivity

1. Measure the diameter of a wire, calculate its cross-sectional area. 2. Connect the wire in a circuit, measure length, voltmeter, and ammeter readings. 3. Calculate resistance using R=V/I for various lengths. 4. Plot resistance against length, find the gradient to determine resistivity.

Q1

What equation links the resistance of a wire to its resistivity?

undefined

R = ρ * (L/A)

Q2

Explain the difference in resistivity between glass and aluminum in terms of charge carriers.

undefined

Glass has a high resistivity due to fewer free charge carriers, while aluminum has low resistivity because it has many free charge carriers.

Q3

What is Ohm’s law?

undefined

Ohm’s law states that the current flowing through a conductor is directly proportional to the voltage applied across it, given a constant temperature.

Q4

How can you experimentally determine the resistivity of a metal?

undefined

To find the resistivity of a metal, one can measure the length and cross-sectional area of the metal wire, apply a known voltage, measure the current, and then use the formula ρ = R * (A/L) to calculate the resistivity.