Study Material and Notes of Ch 14 Chemical Effects of Electric Current Class 8th Science
Topics in the chapter
• Introduction
→ Good Conductor
→ bad Conductor
• Electrolyte
• Magnetic effect of current
• Electroplating
Introduction
→ Materials, which allow electric current
to pass through them, are good
conductors of electricity.
→ Materials, which do not allow electric current to pass through them easily, are poor conductors of electricity.
→ Metals such as copper and aluminium conduct electricity whereas materials such as rubber, plastic and wood do not conduct electricity.
Good conductor
|
Poor conductor
|
| Lemon Juice | Coal Tar |
| Vinegar | Distilled Water |
| Acid solutions | Honey |
| Basic solutions | Vegetable oil |
| Salty water ( Tap water, sea water) | Kerosene |
Electrolyte
→ Conducting liquids are also called electrolytes.
→ The electric current passing through a conducting liquid (electrolyte) causes chemical reactions (electrolysis).
→ A chemical reaction takes place when electric current passes through a conducting solution.
Magnetic Effect of current
→ The bulb will glow or the magnetic needle will show deflection if the liquid in the beaker is a good conductor of electricity.
→ Greater the deflection of needle or brighter the light, better is the conductivity of the liquid.
→ A greenish-blue spot on the potato around the positive electrode is seen if current is passed through wire.
→ The chemical effects of electric current are used in the working of electrochemical cells.
→ Electrochemical cells which generate current are called voltaic cells or galvanic cells.
→ Common batteries also consist of one or more such cells.
Electroplating
→ Electroplating is the process of coating a metal using electric current and electrolyte.
→ The above picture explains how copper can be deposited on a different metal using electroplating.
→ Electroplating can be used to give shiny and scratch proof finish (properties of chromium) to objects made from cheaper metals.
