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In Some Old Texts It is Mentioned that 4π Lines of Force Originate from Each Unit Positive Charge. Comment on the Statement in View of the Fact that 4π is Not an Integer. - Physics

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प्रश्न

In some old texts it is mentioned that 4π lines of force originate from each unit positive charge. Comment on the statement in view of the fact that 4π is not an integer. 

एका वाक्यात उत्तर
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उत्तर

4π is the total solid angle. "4π lines of force" is just a way of stating that the field lines extend uniformly in all directions away from the charge.

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पाठ 7: Electric Field and Potential - Short Answers [पृष्ठ ११९]

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एचसी वर्मा Concepts of Physics Vol. 2 [English] Class 11 and 12
पाठ 7 Electric Field and Potential
Short Answers | Q 7 | पृष्ठ ११९

संबंधित प्रश्‍न

An infinite line charge produces a field of 9 × 104 N/C at a distance of 2 cm. Calculate the linear charge density.


Consider a system of n charges q1, q2, ... qn with position vectors `vecr_1,vecr_2,vecr_3,...... vecr_n`relative to some origin 'O'. Deduce the expression for the net electric field`vec E` at a point P with position vector `vecr_p,`due to this system of charges.


A hollow cylindrical box of length 0.5 m and area of cross-section 25 cm2 is placed in a three dimensional coordinate system as shown in the figure. The electric field in the region is given by `vecE = 20 xhati`  where E is NC­−1 and x is in metres. Find

(i) Net flux through the cylinder.

(ii) Charge enclosed by the cylinder.


When the separation between two charges is increased, the electric potential energy of the charges


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The electric field and the electric potential at a point are E and V, respectively.  


Electric potential decreases uniformly from 120 V to 80 V, as one moves on the x-axis from x = −1 cm to x = +1 cm. The electric field at the origin 

(a) must be equal to 20 Vcm−1
(b) may be equal to 20 Vcm−1
(c) may be greater than 20 Vcm−1
(d) may be less than 20 Vcm−1 


Which of the following quantities does not depend on the choice of zero potential or zero potential energy?


Consider a uniformly charged ring of radius R. Find the point on the axis where the electric field is maximum.

 

A particle of mass 1 g and charge 2.5 × 10−4 C is released from rest in an electric field of 1.2 × 10 4 N C−1. How much is the work done by the electric force on the particle during this period?


An electric field of 20 NC−1 exists along the x-axis in space. Calculate the potential difference VB − VA where the points A and B are
(a) A = (0, 0); B = (4 m, 2m)
(b) A = (4 m, 2 m); B = (6 m, 5 m)
(c) A = (0, 0); B = (6 m, 5 m)
Do you find any relation between the answers of parts (a), (b) and (c)?  


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An electric field  \[\vec{E}  = ( \vec{i} 20 +  \vec{j} 30)   {NC}^{- 1}\]  exists in space. If the potential at the origin is taken to be zero, find the potential at (2 m, 2 m).

 

The electric potential existing in space is \[\hspace{0.167em} V(x,   y,   z) = A(xy + yz + zx) .\] (a) Write the dimensional formula of A. (b) Find the expression for the electric field. (c) If A is 10 SI units, find the magnitude of the electric field at (1 m, 1 m, 1 m).


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(a) (i) What will be the electric field at O, the centre of the pentagon?

(ii) What will be the electric field at O if the charge from one of the corners (say A) is removed?

(iii) What will be the electric field at O if the charge q at A is replaced by –q?

(b) How would your answer to (a) be affected if pentagon is replaced by n-sided regular polygon with charge q at each of its corners?


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