Introduction to Ohm's law

                                                   
What is Ohm's Law ?


In 1826 Georg Simon Ohm discovered that for metallic conductors there is substantially constant ratio of the potential difference between the ends of the conductor.
  Ohm's Law states that the current flowing in an electric circuit is directly proportional to the applied voltage and inversely proportional to the resistance of the material.

Ohm's Law equation

  
I- current

V-voltage

R- resistance

Ohm's law is explained by the following statement.

1. Current varies directly with applied voltage
    A change in the voltage applied to a circuit will  cause the current flowing in the circuit to change.  If the resistance is  constant, the current change will follow the pattern of the voltage change.  Doubling the potential difference doubles the current.

2. Current varies inversely with resistance
   Changing the resistance in a circuit will also cause a change in current flow. if the voltage applied to a circuit is held constant, and the resistance in the circuit is increased. With more opposition to current  flow in the circuit, the circuit current will decrease. On the other hand, if the resistance is decreased the amount of current flow in the circuit will be increased.


3. Voltage vs. current

   The  relationship between voltage
and current can be graphically
 represented with this illustration.

thus:
  1. the higher the voltage, the larger the current
  2.the higher the resistance the lower the current

         AC Ohms Law

Ohms law can also be applied in AC circuits.But alternating voltage and currents are always changing. From zero, current and voltage builds up and reach  its max peak in the positive value at 90 degrees and then back to zero and again to the negative peak value.
In this regard, Its only possible to calculate instantaneous values of voltage and current throughout its cycle.
For AC Ohms law can be expressed by the the same  equation , where R could be replaced by a  inductor or capacitor , where Xc or XL is the AC reactance

Ohms Law Derived formulas formulas from 
Ohms law circle

V= I x R
I=  V/ R
R= V/ I