Two equal and opposite charges separated by a very small distance constitute an electric dipole. A molecule made up of a positive and a negative ion is an example of an electric dipole.
e.g: NaCl,HCl etc..
The product of magnitude of any one of the charges and the length of the electric dipole is called Electric dipole moment.
Vector p= q* 2* vector a
Where 'a' is half the length of dipole. It is a vector quantity, directed from negative to positive charge.
1.10 (a) Electric field at a point on the axial line of an electric dipole
Consider an electric dipole of moment p= 2aq. Let 'S' be a point at a distance 'r' from the center of the dipole.
The field due to an electric dipole is directed from negative charge to positive charge along the axial line.
1.10(b) Electric field due to a dipole at a point on the perpendicular bisector of the dipole(at a point of the dipole ( at a point on the equatorial line)
Consider a dipole of dipole moment p= 2aq.
Let 'S' be a point on its equatorial line at a distance 'r' form its center. The magnitudes of electric field at 'S' due to +q and -q are equal and acts as shown in figure.
To find the resultant electric field resolve vector Ea and vector Eb.
Their normal components cancel each other where as their horizontal components add up to give the resultant field at 'S'.
E= EACos(theta) + EBCos(theta) = 2 EB Cos(theta)
(Since EA=EB)
The direction of the field due to the dipole at a point on the equatorial line is opposite to the direction of the dipole moment.
Electric field due to a point charge varies inversely as the second power of distance 'r' whereas the electric field due to a dipole varies inversely as the third power of distance 'r'
Note:
If the electric field at all points in a region has the same magnitude and same direction then that electric field can be called a uniform electric field.
e.g: NaCl,HCl etc..
The product of magnitude of any one of the charges and the length of the electric dipole is called Electric dipole moment.
Vector p= q* 2* vector a
Where 'a' is half the length of dipole. It is a vector quantity, directed from negative to positive charge.
1.10 (a) Electric field at a point on the axial line of an electric dipole
Consider an electric dipole of moment p= 2aq. Let 'S' be a point at a distance 'r' from the center of the dipole.
The field due to an electric dipole is directed from negative charge to positive charge along the axial line.
1.10(b) Electric field due to a dipole at a point on the perpendicular bisector of the dipole(at a point of the dipole ( at a point on the equatorial line)
Consider a dipole of dipole moment p= 2aq.
Let 'S' be a point on its equatorial line at a distance 'r' form its center. The magnitudes of electric field at 'S' due to +q and -q are equal and acts as shown in figure.
To find the resultant electric field resolve vector Ea and vector Eb.
Their normal components cancel each other where as their horizontal components add up to give the resultant field at 'S'.
E= EACos(theta) + EBCos(theta) = 2 EB Cos(theta)
(Since EA=EB)
The direction of the field due to the dipole at a point on the equatorial line is opposite to the direction of the dipole moment.
Electric field due to a point charge varies inversely as the second power of distance 'r' whereas the electric field due to a dipole varies inversely as the third power of distance 'r'
Note:
If the electric field at all points in a region has the same magnitude and same direction then that electric field can be called a uniform electric field.
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