Ohm's Law and Resistivity

Check whether the conductor is ohmic and temperature is constant. Choose V = IR for circuit values or R = ρL/A for material and dimension values. Convert area to m^2. Substitute values with units. Interpret whether larger length increases resistance and larger area decreases it.

Draw a V-I graph with V on the vertical axis and I on the horizontal axis. For an ohmic conductor, show a straight line through the origin. Label slope as R. For non-ohmic behaviour, the graph is curved and V/I is not constant.

Using ρ = RA/L with area in mm^2 without converting to m^2 gives an answer off by a large factor.

Ohm's law states that the current through a conductor is directly proportional to the potential difference across it, provided temperature and other physical conditions remain constant. Resistivity is the material property that measures how strongly a substance opposes current flow.

Ohm's law states that the current through a conductor is directly proportional to the potential difference across it, provided temperature and other physical conditions remain constant. Resistivity is the material property that measures how strongly a substance opposes current flow. Ohm's law: V = IR, where V is potential difference in volt, I is current in ampere, and R is resistance in ohm. Resistivity relation: R = ρL/A, where ρ is resistivity in ohm metre, L is length in metre, and A is area in m^2. Microscopic form for metals: ρ = m/(ne^2τ). Use Ohm's law only when temperature, strain, and other physical conditions are constant. A nichrome wire shows higher resistance than a copper wire of the same length and area because nichrome has greater resistivity. This is why nichrome is used in heating elements.

For an ohmic conductor at constant temperature, V/I remains constant and is called resistance R. Resistance depends on dimensions, while resistivity depends on the material and temperature. In the microscopic model of a metal, resistivity is related to electron mass, number density, charge, and relaxation time by ρ = m/(ne^2τ). For metals, resistivity generally increases with temperature because collisions become more frequent and relaxation time decreases. Ohm's law: V = IR, where V is potential difference in volt, I is current in ampere, and R is resistance in ohm. Resistivity relation: R = ρL/A, where ρ is resistivity in ohm metre, L is length in metre, and A is area in m^2. Microscopic form for metals: ρ = m/(ne^2τ). Use Ohm's law only when temperature, strain, and other physical conditions are constant. A wire of length 2.0 m and area 0.50 x 10^-6 m^2 has resistivity 1.7 x 10^-8 ohm m. Its resistance is R = ρL/A = (1.7 x 10^-8 x 2.0)/(0.50 x 10^-6) ohm = 0.068 ohm. If 0.34 V is applied, current I = V/R = 0.34/0.068 = 5.0 A. It is commonly asked as a statement of Ohm's law with conditions, V-I graph interpretation, resistance-resistivity distinction, or numerical problems involving R = ρL/A and V = IR. Using ρ = RA/L with area in mm^2 without converting to m^2 gives an answer off by a large factor.