# What is the relation between Electrical and Thermal Units?

### Relation between Electrical and Thermal Units:

In this short post let us discuss about the relation between Electrical and Thermal Units.

#### Joule's Law of Electric Heating:

The amount of work done or energy required to maintain a current of 1 amperes passing through a resistance of R ohms for 1 second is
Workdone = (I2R).t  joules
= VI.t  joules    [We know that V = IR as per Ohms law]
= V2t/R   joules  [ As I  = V/R ]
= W.t  joules    [As V2/R = W ]

The work done is converted into heat H = Work done/ Mechanical equivalent of heat
H = W.D / J
where J = 4200 joules/K cal.
H = (I2R.t / 4200 ) K cal.
= (VI.t / 4200 ) K cal.
= (V2t / R x 4200 ) K cal.
= (W.t / 4200 ) K cal.
Also 1KWH = 860K cal.

#### Relation between Electrical and mechanical units:

1 horse power ( metric) = 75 m-kg/sec.
ie,
1 horse power ( metric) = 75 x 9.81
ie,
1 horse power ( metric) = 735.5 J/sec.
Therefore
1 HP = 735.5 watts.

Thanks for reading about the relation between Electrical and Thermal Units... Please leave your comments below... Please subscribe to get new posts to your mail ID.....

#### You may also like to read:

You might have landing this page because you might have searched like... Relation between Electrical and mechanical units... What is the relation between Electrical and Thermal Units?

### 1 Response

1. Quinten says:

I'm a first year apprentice Electrician, and everything we have been given to study and base our calculations on says that 1 HP = 746 W. You say it's 735.5 and now I'm confused again

This site uses Akismet to reduce spam. Learn how your comment data is processed.