Friday, February 19, 2010
Effects Of An Electric Current
-Electrical energy can be transformed into other forms of energy to produce many effects.
Heating Effect Of A Current
-When a current passes through a wire, the wire heats up. This is caused by the conversion of electrical energy into heat energy. The heat produced depends on the resistance of the wire.
Heating appliances usually have coils of wires or heating elements inside.
These heating elements are made of high resistance materials such as nichrome.
The heating elements heat up when current is passed through them.
Magnectic effect of a current
If an iron rod is placed inside the coil of wire, it makes the magnetic field a few hundred times stronger. When the current is switched off, the iron loses its magnetism. This set-up is known as electromagnet, and it is used in many applications. It gives a magnetic field that can be switched on and off when desired.
Applications of the magnetic effect of current
-A giant elecromagnet can be used to separate iron from non-iron scrap, to be recycled. The electromagnet can also be used to lift heavy iron and steel objects.
-A telephone makes use of a small electromagnet in the speakers and microphones.
-Electric motors, run by electromagnets, are used in many household appliances such as fans, and to run electric trains. A coil of wire wound a round a soft iron core is placed in between the poles of a permanent magnet. When a current passes through the coil, it becomes an electromagnet. It then spins under the influence of the magnetic field of the permant magnet. This set-up is called motor.
Chemical Effect of a current
-Liquids that allows electricity to pass through them are called electrolytes.
-The chemical decomopsition of an electrolyte by an electric current is called electrolysis.
-The two wires or plates through which current enters and leaves the electrolyte are called electrodes.
Application of the chemical effect of current
-Electrolysis is used in a process called electroplating. In this process, the flow of current causes a thin layer of metal to be deposited on the object to be electroplated.
-Electrolysis is also used in industries to extract metals such as aluminium from their compouds. To extract a metal, a solid compound of the metal is heated until it melts. An electric current is then passed through this molten compound. For example, aluminium is obtained from molten aluminium oxide.
9:55 PM
