Electric Field
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Electric Point Charge


A particle, with mass m and charge q, was placed at a point A of an electric field where the vector of the electric field is vertical, pointing upwards and has magnitude E. If we know E, m, and g (free-fall acceleration), determine:
a) The charge q, knowing that the particle is in equilibrium at point A;
b) The sign of the electric charge.

Electric Charge Density


The ratio between the electric charges of two spheres is 3/4, the ratio between its radii is 5/8. Determine the ratio between the densities of electric charge.

Discrete Distribution of Electric Charges


Determine the electric field of a dipole at the points located on the perpendicular bisector of the dipole. Check the solution for points far from the center of the dipole.

Determine the electric field of a dipole at the points along the straight line joining the two charges of the electric dipole.

Two equal charges of the same sign are separated by a distance 2d. Calculate the magnitude of the electric field at the points along the perpendicular bisector of the line joining the two charges. Check the solution for points far away from the center of the charges.

Two equal charges of the same sign are separated by a distance of 2d. Calculate the magnitude of the electric field at the points along the line joining the two charges. Check the solution for points far from the center of charges.

Two point charges of 5×10−6 C and 3×10−6 C, are placed in two vertices of an equilateral triangle of sides equal to 1.2 m. Calculate the magnitude of the electric field in the third vertex, assuming they are in the vacuum.

Four positive charges equal to Q, are placed on a horizontal plane in the vertices of a square of side d.
a) Find the magnitude of the electric field at a point P above the center of the square at a distance equal to d. Assume that the Coulomb constant is equal to k0.
b) If a charge Q < 0 is placed in P, find the magnitude of the electric force will act on this charge.
Solution

Suggestion: compare with simillar problem of  Coulomb's Law.
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