Electricity:- Part 4

Heating effect of electric current 

-> When the ends of a conductor are connected to a battery then free electrons move with drift velocity and electric current flows through the wire. These electrons collide continuously with the positive ions of the wire and thus the energy taken from the battery is dissipated. 

  To maintain the electric current in the wire, energy is taken continu0usly from the battery. This energy is transformed to the ions of the wire by the electrons. This increased the thermal motion of the ions. 

 As a result, the temperature of the wire rises. So, The effect of electric current due to which heat is produced in a wire when current is passed through it is called heating effect of electric current or joule heating. 

 In 1841, joule found that when current is passed through the conductor then the heat produced across:- 

* Directly proportional to the square of the current through the conductor                      i.e. H ∝ I2 

* Directly proportional to the resistance of the conductor i.e. H ∝ R 

* Directly proportional to the time for which the current is passed 

     i.e.H ∝ t 

Combining the above three relations, We get

                         

Electrical Power 

-> The rate of change of doing electric work per unit time is called electrical power. 

                             Or 

The rate of change in electrical energy with respect to time is called an electrical power. i.e.

                        

Unit of power 

-> SI unit of power is W(watt) or J/S and CGS unit of power is erg/sec. 

Other units:-

* 1 KW = 103 W 

* 1 MW = 106 W 

* 1 hp (horsepower) = 746 W 

                 ↓

     it is called the BRITISH unit of electric power.

-> 1 W = The power consumed by a source is said to be one watt if one ampere of current flows through it under a potential difference of 1 volt. So,

                         

Other formulas of electric power