Electrical conductivity of Iodine|Copper|Zinc|Aluminum Foil|Plastic|Plastic Ruler|Rubber|Graphite|Hydrochloric Acid|Sodium Chloride|Sodium Chloride Crystals|Acetone and Ethanol
Aim / Objective:
To investigate the electrical conductivity of various substances
•Electrical Conductivity is defined as the measure of a substance/materials ability to transport of an electric charge or current. It is represented by the Greek letters- σ (sigma), κ (kappa), or γ (gamma).
•When a difference of electrical potential is placed across the conductor, an electric current appears. Conductors such as metals have high conductivity while insulators like that of glass have low conductivity.
•Electrical resistivity measures how strongly a material/substance opposes the flow of electric current. It is represented by the Greek letter ρ (rho), the lower the resistivity the more readily the substance will allow the flow of electric charge.
The following table shows the electrical conductivity and electrical resistivity of various materials
electrical circuit, electrolytic cell, samples of metals (copper (Cu), Zinc (Zn), aluminum oil (Al), Samples of non-metals (iodine (I), plastic, rubber, plastic ruler, graphite ), sodium chloride crystals (NaCl), aqueous sodium chloride (NaCl), dilute hydrochloric acid (HCl), organic solvents (ethanol & acetone)
Method / Procedure:
- Draw a table with three columns, with the names of the test samples in the first column.
- Label the second column “Predictions”, and indicate whether the test samples are conductors or insulators based on your previous knowledge.
- Label the third column as “Results”.
- Connect the circuit as shown in the diagram to determine which of the test samples are electrical conductors.
For the solid test samples, use circuit 1. For liquid samples, use circuit 2.
- Record test results in the third column of the table.
- Compare test results with your predictions.
1.Define electrical conductors:
>>> Electrical Conductors are substances which allow a current to flow through them eg. Graphite while insulators do not allow the passage of an electric current. Eg. plastic.
2. Identify and differentiate between the two types of conductions?
>>> There are two types of conductions; metallic conduction and electrolytic conduction. Metallic conduction involves the flow of free electrons through a metal; these electrons are present in the electron pool and the metal remains chemically unchanged after an electric current is passed through. Electrolytic conduction involves the movement of free ions through a molten substance or solution.
3. Explain why solid ionic compounds do not conduct electricity?
>>> these compounds do not conduct electricity in their solid state because the ions are rigid an tightly held in a crystal lattice and are not able to move. However in its molten state or in a solution the lattice is broken down and the ions are free to move, an example of this is Sodium Chloride crystal.
4. Explain why insulators do not conduct electricity?
>>> They do not conduct electricity simply because of the absence of ions, for when ions are set free they move to an oppositely charged electrode when a voltage is applied. Insulators usually contain molecules.
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