Chemical Effects of Electric Current Class 8 Notes Science Chapter 11

Facts that Matter

• Good conductors of electricity are materials that allow electric current to flow through them easily, such as metals like copper and aluminium.
• Poor conductors of electricity do not let current pass through easily. Examples include rubber, plastic, and wood.
• The filament in a bulb tester heats up and glows because of the heating effect of electric current.
• If the current in a circuit is too weak, the filament won't heat up enough and won’t glow.
• LEDs can replace traditional bulbs in testers as they glow even with weak electric currents.
• A tester can also be made using a compass needle because electric current creates a magnetic effect, causing the needle to move even with small currents.
• Distilled water does not conduct electricity well because it lacks dissolved salts. In contrast, tap water, well water, and pond water contain salts and impurities, making them better conductors.
• Most liquids that conduct electricity are solutions of acids, bases, and salts.
• Chemical effect of the electric current: When an electric current passes through a conducting solution, it causes a chemical reaction. This can lead to gas bubbles forming on electrodes, metal deposits, or colour changes in solutions.
• Electroplating: This is the process of applying a layer of metal onto another material using electricity. It is a common use of the chemical effects of electric current.
• Uses of Electroplating:Electroplating is widely employed in industry to coat metal items with a thin layer of another metal. This can be done to:
  • Make objects look shiny,
  • Prevent corrosion,
  • Make items resistant to scratches,
  • Coat less reactive metals with more reactive ones to protect them from damage,
  • Electroplate cheaper metals with silver or gold to create attractive ornaments.

For example:

• Chromium has a shiny look, resists corrosion, and is scratch-resistant. However, it is expensive, so cheaper metals like those used in taps and car parts are electroplated with chromium.
• Jewellery made from inexpensive metals can be electroplated with silver or gold to appear more valuable.
• Tin is less reactive than iron, so food cans made of iron are electroplated with tin to avoid spoilage.
• Iron used for bridges and cars is coated with zinc to protect against corrosion and rust.