Chemical Effect of electric current|how to generate electricity?

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Electroplating,Electrolysis,ElectrorefiningElecteometallurgy

- Electric Charge

        • All matter is made up of very small particles called atoms. Atoms are made up of even smaller particles called protons, neutrons and electrons. These particles possess several properties. One of these properties called electric charge. Neurons are the neutral, i.e.they do not possess any charge, the protons have positive (+) charge, and the electrons have negative charge(-). 

 • Since atoms have equal number of protons and electrons, their positive and negative charges cancel each other and so atoms do not have a charge. 

 • An object becomes positively charged when it loses electrons and becomes negatively charges cancel each other other and so atoms do not have a charge. 

 • Objects can become charged by friction, conduction, and induction. 

Conductors & Insulators

        In some atoms, the electrical force is not strong enough to hold the electrons to the nucleus. Consequently, the electrons are able to move freely in the material. 

 • Materials in which electrons can move easily are called good conductors. 

    Material in which electrons cannot flow freely are called bad conductors or insulators. 

 • Copper, Aluminum and mercury are good conductors. Plastic, rubber, glass, wood and air are good insulator. All gases are bad conductors of electricity. 

 • Liquids are bad conductors of electricity. Kerosene, petrol, alcohol and vegetables oil are bad conductors of electricity. Pure water is a now conductors of electricity. Impure water is a good conductors of electricity. Pure water which is a bad conductors of electricity, becomes a conductors of electricity on adding acids, bases and salts to it. 

For example:- (a) A solution of acids like sulphuric acid (H2SO4) and hydrochloric acid (HCL) conducts electricity. 

  (b) :- A solution of sodium hydroxide (NaOH) or any other base soluble in water conducts electricity.

  (c) :- Common Salt (sodium hydroxide) or any other salt when added to pure water makes it conductors of electricity. 

Electric Current

       Electric current is the flow of electric charge and is measured by the rate of flow of charge.

Difference in the conduction of electricity in solids and liquids. 

     1:- Electricity is carried by free electrons in solids while in liquids electricity is caused by the movement of positive and negative ions. When a part of a molecule of a liquid gains an electron we call it a negative ion, and when it loses an electron, we call it a positive ion. Negative ions are also called anions and positive ions are called cation. 

  (2) :- When electricity passes through a solid, no chemical change takes place nut when electricity passes through a liquid, then a chemical change take place. 

   For example, when electricity is passed through acid- solution, then water is decomposed into hydrogen and oxygen gases.

 

LED (Light Emitting Diode) 

      It is a semi- conductors device which glows even a very weak current passes through it. It has two (called leads) one of these being longer than the other. While connecting LED in a circuit, the longer lead is always connected to the positive terminal of the battery and the shorter lead to the negative terminal. 

A LED may be used in place of an electric buld in the tester. It would glow even when the current is weak. 

Electrolyte 

      • The liquids that are good conductors and are thus able to conduct electricity are called conducting liquids or electrolytes. An electrolyte undergoes partial or complete dissociation into ions (positively charged ions and negatively charged ions) and the electricity is conducted in the solution by the flow of these ions. 

      • A strong electrolyte is one which contains a lot of ions in it and so conducts electricity very well. 

   A  𝘸𝘦𝘢𝘬 𝘦𝘭𝘦𝘤𝘵𝘳𝘰𝘭𝘺𝘵𝘦 is one which  contains less and so, is not able to conduct electricity very well. For example :- Vinegar, lemon Juice, Tap water and Rain water are the weak electrolytes. 

Non- Electrolyte

        Liquid or solutions which are non- conductors of electricity are called Non- Electrolyte. They do not undergo any chemical change when electric current is passed through them. 

For example, :- Distilled water, kerosene, petrol, Alcohol, vegetable oils (mustard oil) are all non- electrolytes. 

Solid Electrical Conductors

   • Electrode :- A solid conductors like a peace of metal on carbon, through which an electric current enters or leaves a liquid or gas, is called an  𝘦𝘭𝘦𝘤𝘵𝘳𝘰𝘥𝘦. 

   • Anode :- There are two types of electrodes- positive electrode and negative electrode. The positive electrode is called an anode. An anode has a positive charge because it is connected to the positively charge end of an external power supply. 

   • Cathode :- The electrode having negative charge is called cathode. It has a negative charge because connected to the negatively charged an external supply. 

Generating Electric Energy 

     Energy cannot be created or destroyed. It can only can be converted from one kind to another. There are many device which convert other types of energy to electrical energy. This, generators convert mechanical energy into electrical energy. Cells change chemical energy into electrical energy. Batteries are made of two or more cells battery is used when we require more electricity. Solar cells convert sunlight into electrical energy. 

Any that device that produce an electric current is called a source of electric current. 

Cells & Batteries 

     • Cells are two types : primary and secondary. Primary cells cannot be charged. Hence, they are discarded after use. Secondary cells are are rechargeable. About 80% of rechargeable batteries are currently composed of Nickel & Cadmium. 

     • An electric cell contains a mixture of chemicals called an electrolyte. Electrolyte are substances that can conduct an electric current when they are in solution. Every cell has a pair of electrodes made from conducting materials. An electrode is the part of the cell through which charges enter or exit. 

     • Chemical changes between the electrolyte and the electrode convert chemical energy into electrical energy. 

     • Two kinds of cells are wet cells and dry cells. 

 - Dry cells

DRY CELL

        A dry cells is a primary cell. Dry cells work in a similar way. But the electrolytes in dry cells are solids or paste like. The cells used in torches, clocks, etc,. Are dry cells. 

 A dry cell shown in the figure consists of a cylindrical zinc container. It's base acting as the negative electrode. It has a carbon rod placed at the centre and a brass cap. Tha carbon rod acts as the positive electrode and is surrounded by a mixture of manganese dioxide (MnO2) and charcoal (C). The electrolyte used is a moist paste of ammonium chloride (NH4Cl), plaster of Paris (POP) . The outer body (except the base) is insulated with a thick cardboard or plastic material. 

   • when the bulb is connected to a bulb, the slow ongoing chemical chemical reaction in the cell becomes fast and start the flow of electric current through the bulb. As a result, the bulb starts glowing. If more such cells are connected in the series the greater electrical energy will be generated. 

 Wet cells

Wet Cell

    A wet cell is a secondary cell. A car battery uses wet cells. The figure shows a wet cells using sulphuric acid as the electrolyte. Two metal strip of zinc and copper are suspended in the acid. 

  • When the metal strips are connected by a metallic  wire the electric current begins to flow through the wire. It happens because of chemical changes between electrolyte and the electrodes that convert chemical energy into electrical energy. 

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