What is electrical resistivity of a material? What is its unit? Describe an experiment to study the factors on which the resistance of conducting wire depends.


Resistivity is an inherent property of a conductor which resists the flow of electric current. The resistivity of each material is unique. SI unit of resistance is Ωm.

Experiment to study the factors on which the resistance of conducting wire depends.

Take a nichrome wire, a torch bulb, a 10 W bulb and an ammeter (0 – 5 A range), a plug key and some connecting wires.

  • Set up the circuit by connecting four dry cells of 1.5 V each in series with the ammeter leaving a gap XY in the circuit, as shown in Figure.
  • It is observed that resistance depend on the material of the conductor
  • Length of conductor determines the resistance
  • Resistance depends on the area of cross-section.

  • Complete the circuit by connecting the nichrome wire in the gap XY. Plug the key.
  • Note down the ammeter reading. Take out the key from the plug.
  • Replace the nichrome wire with the torch bulb in the circuit and find the current through it by measuring the reading of the ammeter.
  • Now repeat the above step with the 10 W bulb in the gap XY.
  • Are the ammeter readings different for different components connected in the gap XY? What do the above observations indicate?
  • You may repeat this Activity by keeping any material component in the gap. Observe the ammeter readings in each case. Analyse the observations.

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