Unit 4 - Revision Summary: Effects of Electric Current

Electric current has three effects:
A. Heating
B. Chemical 
C. Magnetic

A. Heating: W = I2Rt

This apparatus can be used to demonstrate the heating effect

Joule’s Law 
The rate at which heat is produced in a resistor is proportional to the square of the current flowing through it, if the resistance is constant. P µ I2

Verification of Joule’s Law

Advantage of use of EHT in transmission of electrical energy
Since P = VI, if V is large, I can be kept small.
The power loss in the cable due to heating is given by I2 R.
Therefore, for a given cable resistance: the higher the voltage (hence the smaller the current), the smaller the power loss.

B. Chemical effect of electric current

The passage of an electric current through a liquid causes chemical changes; the process is known as electrolysis.

Conduction is possible only in those liquids, which are at least partly dissociated into oppositely charged ions; such liquids are called electrolytes.

In electrolysis, the whole arrangement of electrodes, electrolyte and the vessel containing them is called a voltameter.

Electroplating is a common application of electrolysis.

C. Magnetic effect of electric current

The magnetic effect of an electric current was discovered by Hans Christian Oersted in 1820.

Applications
The magnetic effect of an electric current has many applications, e.g. in electromagnets, electromagnetic relays, loudspeakers, electric motors, ammeters, voltmeters, etc

Well done! You have completed Unit 4.
Now go back to theUnit 4 Home Page ,
or start Unit 5- Quantity of Heat