Saturday, August 25, 2012

Direct current (3) 'Ohm's law'

Ohm's law

In our previous post, we discussed about the resistance. Today we are about to study the Ohm's law.

Whenever electric current flows through a conductor , the following factors are present :

  1. The potential difference V across the conductor causing the current to flow.
  2. The opposition or resistance R of the conductor which must be overcome.
  3. The current I which in the conductor as a result of pressure overcoming the resistance.
The relationship between these three quantities are defined in Ohm's law.

Ohm's law:
The voltage difference across a conductor is directly proportional to the current which goes through it due to the voltage difference , provided the temperature of the conductor does not change.


The ratio of potential difference  V between any two points of a conductor to the current I flowing between them is constant, provided the temperature of the conductor does not change.


V/I = constant
V/I = R

where R is the resistance of the conductor between the considered points.

This can be written as, 
V = IR

This law is applicable to both DC and AC circuits. But it is complicated than DC .

Derived relations from Ohm's law

  • Power is given by the product of voltage and current.

    W = VI
    Using ohm's law we can rewrite this equation as,

     W = I2
     W = V2/R

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