Factors on which the resistance of a conductor depends

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1. Electricity Factors on which the resistance of a conductor depends Presentation compiled by: Dhananjay M.R

2. Resistance: The electrical resistance of an object is a measure of its opposition to the flow of electric current Resistivity: Resistivity is the characteristic property of the material by which it resists the amount of current through it. Both the resistance and resistivity of a material vary with temperature.

3. Resistivity Resistivity is the characteristic property of the material by which it resists the amount of current through it It depends upon the nature of the material and materials and physical conditions like temperature SI Unit: Ohm-meter It is denoted by ρ (Rho).

4. Resistance The electrical resistance of circuit is a measure of its opposition to the flow of electric current. SI Unit: Ohm ( Ω  ) It is denoted by R

5. Conductors, Alloys & Insulators Conductors refer to certain kind of materials or objects that permits the flow of electric current (charge) in one or more than one direction. EG. Metals, Electrolytes etc.  Insulators refer to the material which doesn't allow electricity and to pass from it. EG. Pin insulators, Suspension insulators, wood, rubber etc. An alloy is a substance which is formed when two or more metals are combined. They can also be formed when metals are combined with other elements.  EG. brass, pewter, phosphor bronze, amalgam, and steel.

6. Properties of Resistance in a Conductor The resistance of a conductor depends on varies properties, such as: The Length of the conductor The area of its cross-section The nature of its material Accurate measurements have proven that the resistance of a uniform metallic conductor is directly proportional to its length and inversely proportional to the area of its cross-section.

7. Properties of Resistance in a Conductor The resistance of a conductor depends on varies properties, such as: The Length of the conductor The area of its cross-section The nature of its material Accurate measurements have proven that the resistance of a uniform metallic conductor is directly proportional to its length(l) and inversely proportional to the area of its cross-section(A). R  ∝ l(Length) R  ∝ 1/A(Area of Cross-section)

8. Properties of Resistance in a Conductor The resistance of a conductor depends on varies properties, such as: The Length of the conductor The area of its cross-section The nature of its material Accurate measurements have proven that the resistance of a uniform metallic conductor is directly proportional to its length(l) and inversely proportional to the area of its cross-section(A). R  ∝ l(Length) R  ∝ 1/A(Area of Cross-section) R =  ρ x l/A, ρ(rho)* ρ  = constant of proportionality

9. Sums

10. Q1 . How much current will an electric bulb draw from a 220 V source, if the resistance of the bulb filament is 1200 Ω? Solution: We are given, V = 220 V  R = 1200 Ω We need to find current We know that I=V/R, We get: I = 220 V/1200 Ω  I= 0.18 A

11. Q2 .   How much current will an electric heater coil draw from a 220 V source, if the resistance of the heater coil is 100 Ω?  Solution: We are given ,  V = 220 V, R = 100 Ω. We need to find current We know that I=V/R, We get: I = 220 V/100 Ω  I = 2.2 A.  Note the difference of current drawn by an electric bulb and electric heater from the same 220 V source! 

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