Chemical Effects of Electric Current Summary Class 8 NCERT Summary Chapter 11

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.

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.

• A coating of zinc is deposited on iron to protect it from formation of rust.