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

Resistance

Resistance

Chapter : Electric

Topic : Resistance

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