Category :
8th Class
Chemical Effects of Electric Current
Synopsis
- Materials which allow electric current to pass through them are good conductors of electricity, e.g., Metals.
- Materials which do not allow electric current to pass through them are bad conductors of electricity, e.g., Wood, Plastic, etc.
- Human body is a good conductor of electricity. Thus, we should take precautions while handling electrical appliances.
- A bulb glows due to the passage of electric current since the filament of the bulb is heated to a very high temperature. However, if the current through a circuit is too weak/the filament does not get heated sufficiently and it does not glow.
- An LED (Light Emitting Diode) glows even when a weak (small) electric current flows through it.
- Electric current produces a magnetic effect. It causes a compass needle to deflect.
- Pure water (distilled water) is a poor conductor of electricity.
- Most liquids that conduct electricity are solutions of acids, bases and salts.
- The passage of an electric current through a conducting solution causes chemical reactions. As a result any of the following activities can be observed.
(a) Formation of gas bubbles.
(b) Deposit of metals on electrodes.
(c) Change in colour of the solution.
- When electricity is passed through some substances, they decompose. Such reactions are called electrolytic reactions. This chemical effect is used to extract elements in metallurgy and for electroplating.
- The process of depositing a layer of any desired metal on another metal by passing electricity is called electroplating.
- Chromium plating is done to make the object scratch proof and shiny.
- Tin cans used to preserve food items/soft drinks are made by electroplating tin onto iron.
- A coating of zinc is deposited on iron to protect it from corrosion and rust.
- CFLs (Compact Flourescent Light) consumes less electricity as compared to electric bulb and LED's, but contains mercury which is toxic and poses a disposal problem.
