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Resistivity

R=ρ L
  A
resistance= resistivity × ;length(m)          
 cross-section area(m2).
ρ is resistivity, L is the length of the wire and A is the cross-sectional area of the wire.Resistivity is a property of the material.ρ units are ohm metre (Ω m)

Measuring ResistivityMeasure diameter of wire using micrometer.Take measurements at several different points and calculate the mean.Calculate the area using π(diameter/2)2Measure the length of wire with a metre rule.Calculate the resistance from p.d. and current for different lengths.Plot a graph of resistance against length of wire.Resistivity ρ = gradient x A (cross-section area)

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Specification: AQA Physics (7407), AS-level, 3.5.1.3 Resistivity. Topic: Electric Current.

Key terms in this lesson

Potential difference
The energy transferred per unit charge as charge moves between two points in a circuit.
Resistance
The ratio of the potential difference across a component to the current flowing through it, measured in ohms.

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