Ley de Ohm I

Ohm's Law,
Example One
The circuit below is called a Wheatstone bridge. It is used for measuring resistance. Show that when the current through the galvanometer G is zero, then R₁ = R₂(R₃/R₄). Thus, if we know R2 and the ratio (R₃/R₄), we can obtain the resistance R₁.

I_G = 0 means points C and D are at the same potential and
that I₁ = I₂, I₃ = I₄.

By Ohm’s law V_AC = I₁R₁, V_AD = I₃R₃, V_CB = I₂R₂, V_DB = I₄R₄.

As V_AC = V_AD and V_CB = V_DB, then I₁R₁= I₃R₃,
I₂R₂= I₄R₄.

As I₁ = I₂ and I₃ = I₄, then doing I₁R₁/ I₂R₂=I₃R₃/I₄R₄ we get R₁= R₂(R₃/R₄)