Electric charges and fields

Electric Charges and Fields

  
 Problems

Question1. The charged particle, of charge 2 μC and mass 10 milligrams, moving with a velocity of 1000 m/s entres a uniform electric field of strength 103 NC-1 directed perpendicular to its direction of motion. Find the velocity and displacement, of the particle after 10 s.

Solution. The velocity of the particle, normal to the direction of the field.

                  Vx = 1000 ms-1,       is constant

The velocity of the particle, along the direction of the field, after 10 s is given by



Question2. Assuming that the charge on an atom is distributed uniformly in a sphere of radius 10-10m, what will be the electric field at the surface of the gold atom? For gold, Z = 79.

Solution. The charge may be assumed to be concentrated at the center of the sphere of radius 10-10 m.

                                             r = 10-10 m,

                                                q = Ze = 79 × 1.6 × 10-19 C.



Question4. Two-point charges + 4 μC and + 1 μC are separated by a distance of 2 m in the air. Find the point on the line joining charges at which the net electric field of the system is zero.

Solution



Question5. Two-point charges of + 16 μC and -9 μC are placed 8 cm apart in the air. Determine the position of the point at which the resultant field is zero.

Solution.



Question6. Two point charges q1 = ±0.2 C and q2 = ±0.4 C is placed 0.1 m apart. Calculate the electric field at

(a) The midpoint between the charges.

(b) A point on the line joining q1 and q2 such that it is 0.05 m away from q2 and 0.15 m away from q1.  

Solution. (a) Let 0 be the midpoint between the two charges.



Question7. Two-point charges q1 and q2 of 10-8 C and -10-8 C respectively are placed 0.1 m apart. Calculate the electric field at points A, B, and C as shown in the figure.

Solution.


Question8. ABCD is a square of side 5 m. Charges of + 50 C, - 50 C, and + 50 C are placed at A, C, and D respectively. Find the resultant electric field at B.

Solution.




Question9. Four charges +q, +q, -q, -q, are placed respectively at the four corners A, B, C, and D of a square of side ‘a’. Calculate the electric field at the center of the square.

Solution.



Question10. Two-point charges + 6q and - 8q are placed at the vertices ‘B’ and ‘C’ of an equilateral triangle ABC of side ‘a’ as shown in the figure. Obtain the expression for,

(I) The magnitude and

(ii) The direction of the resultant electric field at the vertex A due to these two charges.

 











 

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