Using an Ammeter to Investigate if a Substance is a Conductor or an Insulator
A
Procedure Set up circuit as illustrated in Fig 17.1. Connect the crocodile clips to substance 1, close the switch and note current using the ammeter.
Repeat the process using different substances to be tested.
Fig 17.1
Apparatus Battery, leads, crocodile clips, ammeter, switch, various substances
Observation The current will differ greatly depending on the substance connected to the crocodile clips.
Conclusion Certain materials are better conductors than others.
Effects of an Electric Current There are three effects of electric current: (i) chemical, (ii) magnetic and (iii) heating.
Chemical Effect An electric current can cause a chemical reaction. The chemical effect of an electric current is called electrolysis.
SCIENCE,TECHNOLOGY & SOCIETY
Electrolysis of water Water can be broken up into its constituent elements of hydrogen and oxygen by electrolysis. Using the Hoffman voltameter (Fig 17.2), hydrogen ions are attracted to the cathode and oxygen to the anode.
Everyday example of the chemical effect Electroplating is the covering of one metal with a thin layer of another. This technique may be used to coat iron with a rustproof metal such as aluminium; high quality electronic devices use copper which is gold plated to provide a corrosion-resistant electrically conductive layer, or cover a cheap metal with a precious one to improve its appearance.
