RESISTANCE AND CONDUCTANCE

Resistance:

• The property of a material which opposes the flow of current is known Resistance.
• The Units of Resistance is

1.  kilo ohm's.
2. Mega ohm's.
3. Milli ohm's.
4. Micro ohm's. 

• The device used for this purpose is known as a Resistor.
  
• These are widely used in electric circuits.

Law of Resistance:

• Resistance is directly proportional to length of the material.
• Resistance is inversely proportional to area of the conductor

         R=(rho)×(l/a)

 Here,

         rho-Resistivity or specific resistance

         l-length of material

         a-Area of the material.

• The unit of this Resistivity are

1. Ohm's per meter
2. Ohm's per meter cube
3. Ohm's per centimetre
4. Ohm's per centimetre cube

 Where,
          1 ohm per meter=100 ohm's per centimetre

Conductance:

• It is just a reciprocal of Resistance.
• It is the property of a material which allows the flow of current.
• One of the best conducting material is copper.
• The units of this condutance is Mho.
• It id denoted by a letter G

                G=(conductivity)×(a/l)

• The units of this conductivity are mho per meter.