Resistance and Resistivity

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?

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R = ρ * (L/A)

Q2

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

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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?

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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?

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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.