Electrical heating, or

electrical work

 

 

Reason why heating happens:

1) When a potential difference is applied to a conductor, an electric field is develops inside the conductor.



2) And free electrons starts moving from negative end to the positive end.



3) As electron moves and gain a velocity it starts collisions with the metal ions and atoms of the conductor.



4) Due to this collisions ions & atoms gain energy and their vibrational motion increases.



5) this is the real reason why temperature of conductor increases on applying electric field or potential.

 

  

Amount of electric work

 


1) Suppose through a resistor of resistance R, I amount of current is flowing through it, when V amount of potential difference is applied for a time period t,




2) Then amount of charge flow through the resistor is

q = It




3) Now we know that work done on passing these amount of charge is

W = V × q

W = V × (It)

W = VIt

 



But we know from Ohm’s law

V = IR

So,




4) So amount of work done on passing through I amount of current through a resistor of resistance R, on applying V potential for time t, is


            in Joule unit

 



5) we know that    1 calorie = 4.18 Joule

  


this is the amount of heat produce when I amount of current passes through a resistance R for t amount of time.