# Ohms Law – Simon Ohms Amazing Experiment and Results

- Link: https://studyelectrical.com/2015/11/ohms-law-ohms-experiment-and-results.html
- Published: 2015-11-11T13:49:00+00:00
- Author: 

We all learn Ohms law from our elementary school. This a magical formula that solves
most of the problems in electrical engineering. 

Did you know who is George Simon Ohm and how he created this amazing formula? We
will explain it today.

## Ohms Law Statement

We all know Ohm’s Law deals with the relationship between voltage and current in
an ideal conductor.

This relationship states that: The potential difference (voltage) across an ideal
conductor is proportional to the current through it. The constant of proportionality
is called the “resistance”, R. 

Read the difference between [potential difference and Emf.](https://studyelectrical.com/2017/04/electric-potential-difference-and-emf.html)

Ohm’s law states that the current through a conductor between two points is directly
proportional to the voltage across the two points. Introducing the constant of proportionality,
the resistance, one arrives at the usual mathematical equation that describes this
relationship:

**I = V/R**

where I is the current through the conductor in units of amperes, 
 V is the voltage
measured across the conductor in units of volts,  R is the resistance of the conductor
in units of ohms.

More specifically, Ohm’s law states that the R in this relation is constant, independent
of the current.

### Who is Georg Simon Ohm?

Georg Simon Ohm a German physicist investigated the relationship between current
and voltage in a resistor and published his experimental results in 1827.

Georg Simon Ohm (16 March 1789 – 6 July 1854) was a German physicist and mathematician.
As a school teacher, Ohm began his research with the new electrochemical cell, invented
by Italian scientist Alessandro Volta. 

Using equipment of his own creation, Ohm found that there is a direct proportionality
between the potential difference (voltage) applied across a conductor and the resultant
electric current. This relationship is known as Ohm’s law.

## Ohms Experiment

A DC variable supply voltage is connected with a positive terminal at point a and
negative terminal at ‘b’ as shown.

As voltage is increased, the current recorded by the ammeter increases.

For every voltage value, the current is recorded and the corresponding point is 
plotted on the rectangular graph.

![](http://1.bp.blogspot.com/-KsmjzelXQOs/VkM5nWBRiOI/AAAAAAAABl4/PBlGjyYxVbQ/s1600/
Ohms%2Blaw%2Bexperiment%2BSetup.jpg)

Ohms Law Experimental Setup

With this, a straight line graph passing through origin is obtained in the first
quadrant.

Next the terminals of the variable dc supply are interchanged i.e. a is connected
to -ve polarity of DC supply and b is connected to the +ve polarity of DC supply.

Since both the voltmeter and ammeter are moving coil, their individual connection
should also be interchanged so that meters can read upscale. 

This has been done to reverse the direction of flow of current through the resistor
R. Again the voltage is varied and corresponding to each voltage, the current is
recorded and the pairs of V and I are plotted in the third quadrant.

## Experiment Results

The experimental results indicate that there is a linear relationship between the
current and voltage both in the first and third quadrant.

The slope of the straight line is also the same in both the quadrants which shows
that the potential difference across the terminals of the conductor is proportional
to the current passing through it i.e. **V α I**.

[⌊Ohms%2Blaw%2Bresults⌉⌊Ohms%2Blaw%2Bresults⌉[

Also, it is found that for a constant current in the conductor resistance should
be changed proportionally to the potential difference i.e. **V α R**.

Combining the two proportionalities, we have

V α IR

or V= kIR

where k is a constant of proportionality.

However, the units of voltage, current and resistance are defined so that the value
of k = 1. When the current is 1 amp, voltage 1 volt, the resistance is 1 Ω.

1 = k . 1 . 1

Thus the equation becomes

**V= IR**

The equation explains ohm’s law which is stated as follows :

 * The resistances which Ohm considered are linear.
    - i.e. the resistances which have linear V-I characteristic.
 * Also, these are bilateral
    - i.e. irrespective of the direction of flow of current the resistance does 
      not charge.
 * Physical condition (Temperature, Pressure etc.) of the conductor remaining constant,
   the voltage across the terminals of a conductor is proportional to the current
   flowing through it.

 

 

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