## Resistance

 3.2 Resistance

 Ohm's law Potential difference flowing through a conductor is directly proportional to the electric current when the temperature and other physical properties are kept constant. $$V = I\times R$$

If Ohm's law is obeyed, the graph against it or otherwise is a straight line as follows:

 Ohmic conductor Conductor which obeys Ohm's Law (Resistance constant) Example: Constantan wire

 Non-ohmic conductor Conductor which does not obeys Ohm's Law (Resistance constant) Example: Filament bulb

 Resistance of wire $$R=\dfrac{\rho\,l}{A}$$

Factors that affect the resistance of a wire

• Length of wire, $$l$$
• $$l$$ increase, $$R$$ increase
• cross sectional area of wire, $$A$$
• $$A$$ increase, $$R$$ decrease
• resistivity of the wire, $$\rho$$
• $$\rho$$ increase, $$R$$ increase

 Resistivity of a conductor, $$\rho$$ a measure of a conductor's ability to oppose the flow of electric current unit is ohm-meter depends on the temperature and the nature of the conductor material

## Resistance

 3.2 Resistance

 Ohm's law Potential difference flowing through a conductor is directly proportional to the electric current when the temperature and other physical properties are kept constant. $$V = I\times R$$

If Ohm's law is obeyed, the graph against it or otherwise is a straight line as follows:

 Ohmic conductor Conductor which obeys Ohm's Law (Resistance constant) Example: Constantan wire

 Non-ohmic conductor Conductor which does not obeys Ohm's Law (Resistance constant) Example: Filament bulb

 Resistance of wire $$R=\dfrac{\rho\,l}{A}$$

Factors that affect the resistance of a wire

• Length of wire, $$l$$
• $$l$$ increase, $$R$$ increase
• cross sectional area of wire, $$A$$
• $$A$$ increase, $$R$$ decrease
• resistivity of the wire, $$\rho$$
• $$\rho$$ increase, $$R$$ increase

 Resistivity of a conductor, $$\rho$$ a measure of a conductor's ability to oppose the flow of electric current unit is ohm-meter depends on the temperature and the nature of the conductor material