Question

How do we get this equation ?? H=V^2÷R

Answer 1

$H=\frac{V^2}{R}\times t$ is the equation that represents the Joule's law of heating.

Explanation:

Joule's law of heating defines the heat generated by any current flowing conductor is directly proportional to  

1. Square of Current (I²),

2. Resistance of the conductor (R)

3. Time for which current is passed (t)

Hence, Heat generated = $H = I^2 Rt$ .....................(1)

By Ohm's Law, the potential difference (V) across a conductor is directly proportional to the current(I) flowing through it. The constant of proportionality is termed as resistance of the conductor (R).

$V\ \alpha\ I\\V=I\times R$ ...............................................(2)

From (2), Current (I) can be rewritten as

$I = \frac{V}{R}$ ........................................................(3)

Substituting (3) in (1), we get

$H = I^2\times R\times t \\=(\frac{V}{R} )^2\times R\times t\\\\=\frac{V^2}{R^2}\times R\times t = \frac{V^2}{R}\times t\\\\ H =\frac{V^2}{R}\times t$