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As electric flux, φ = E.Δs
∴ unit of φ is N C^{1} m^{2}
The dimensional formula of electric flux is
Electric flux, φ=
The dimension of φ = Dimension of E x dimension of s
[φ] = [M^{1}L^{1}T^{2}][AT]^{1}[L^{2}] = [M^{1}L^{3}T^{3}A^{1}]
A circular plane sheet of radius 10 cm is placed in a uniform electric field of 5 x 10^{5}N C^{1}, making an angle of 60^{0} with the field. The electric flux through the sheet is
Here, r = 10 cm 0.1 m, E = 5 x 10^{5} N C^{1}
As the angle between the plane sheet and the electric field is 60^{0}, angle made by the normal to the plane sheet and the electric field is θ = 90^{0}  60^{0} = 30^{0}
φ_{E} = ES cos θ = E x πr^{2} cos θ
= 5 x 10^{5} x 3.14 x (0.1)^{2} cos 30^{0} = 1.36 x 10^{4} N m^{2}C^{1}
A uniform electric field E = 2 x 10^{3} N C^{1} is acting along the positive xaxis. The flux of this field through a square of 10cm on a side whose plane is paralled to the yz plane is
Here, E = 2 x 10^{3} N C^{1} is along + xaxis
Surface area, s = (10 cm)^{2} = 10^{2 }x 10^{4} m^{2} = 10^{2} m^{2}
When plane is parallel to yz plane, θ = 0°
So φ = E s cosθ = 2 x 10^{3} x 10^{2} cos 0^{°} = 20N C^{1} m^{2}
In the question number 66, the flux through the same square if the line normal to its plane makes a 60° angle with the xaxis is
When normal to the plane makes an angle of 60° with xaxis, then θ = 60°
φ = Es cosθ = 2 x 10^{3} x 10^{2} cos 60° = 10 N C^{1}N C^{1}m^{2}
Which of the following statements about dipole moment is not true?
Dipole moment is a vector quantity and has magnitude of 2qa and it is in the direction of the dipole axis from q to q.
The unit of electric dipole moment is
The unit of electric dipole moment is: 2ql = C − m = Debye
Two charges + 20 μC and 20 μC are placed 10 mm apart. The electric field at point P, on the axis of the dipole 10 cm away from its centre O on the side of the positive charge is
Here, q = ±20μC = ±20 x 10^{6}C, 2a = 10 mm = 10 x 10^{3}m
r = OP = 10 cm = 10 x 10^{2} m
= q x 2a = 20 x 10^{6} x 10 x 10^{3} m = 2 x 10^{7} m
The electric field along BP,
As a < < r,
Consider a region inside which, there are various types of charges but the total charge is zero. At points outside the region
When there are various types of charges in a region, but the total charge is zero, the region can be supposed to contain a number of electric dipoles. Therefore, at points outside the region, the dominant electric field ∝ (1/r^{3}) for large r.
Two point charges of 1μC and 1μC are separated by a distance of 100 Å. A point P is at a distance of 10 cm from the midpoint and on the perpendicular bisector of the line joining the two charges. The electric field at P will be
The Point lies on equatorial line of a short dipole,
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