Problem 71-1    Source:  Example 26-8 - page 810 - KNIGHT, Randall D. -    Book: Física - Uma Abordagem Estratégica - 2ª Edição - Ed. Bookman - 2009.

In a hydrogen atom, the electron describes an orbit with a radius of 0.053 nm around the proton.

a) What is the intensity of the electric field created by the proton at the position of the electron?.

b) What is the magnitude of the electrical force exerted on the electron?

Problem 71-2    Source:  Problem developed by the author of the site.

We see in Figure 71-02.1 the distribution of three particles, Q₁, Q₂ e Q₃, in the x-y plane. If the three particles have the same charge, being equal to + 5 µC, calculate the force, in module and direction, that the particle Q₃ suffers in the presence of the other two.

Problem 71-3    Source:  Problem developed by the author of the site.

Whether it's two charges, q₁ = 20 µC in the coordinate (0,-5) meters and q₂ = - 10 µC in the coordinate (-5,0) meters. Calculate:

a) What is the electric field produced by these charges at the source?

b) The resulting electric field and its angle with the positive x-axis.

Problem 71-4    Source:  Proof 1 - PUCRJ - RJ - 2010.

What happens to two electrical charges, +Q y -q placed at a distance d between each other, if we change the charge + Q by +4 Q, the charge -q by +3 q and the distance d by 2 d?

Problem 71-5    Source:  Entrance Exam - UERJ - RJ - 2018.

The scheme presented in Figure 71-05.1 represents the metallic spheres A and B, both with mass of 10^-3 Kg and electrical charge of module equal to 10^-6 C. The spheres are attached by insulating wires to supports, and the distance between them is 1 meter . Assume that the wire holding the sphere A has been cut and that the resulting force on that sphere corresponds only to the force of electrical interaction. Calculate the acceleration, in m/s, acquired the sphere A immediately after cutting the wire.

Problem 71-6    Source:  Entrance Exam FUVEST - SP - 2019.

Three small spheres charged with positive charge, Q, occupy the vertices of a triangle, as shown in Figure 71-06.1. Inside the triangle, another small sphere is affixed, with negative charge, -q. The distances of this charge to the other three can be obtained from the figure. Calculate the resulting electrical force (in module, direction and direction) on the charge q, knowing that:

     Q = 2 x 10^-4 C,  q = - 2 x 10^-5 C,   x = 6 m,   and  K = 9 x 10⁹ N m²/C²

Problem 71-7    Source:  Entrance Exam FUVEST - SP - 2019.

Two identical spherical metallic objects, containing electrical charges of 1 C and 5 C, are placed in contact and then spaced at a distance of 3 m. Considering the Coulomb constant K = 9 x 10⁹ N m²/C², calculate the force acting between the charges after contact and whether it is of attraction or repulsion.

Problem 71-8    Source:  Adapted of the Problem 76 - page 817 - KNIGHT, Randall D. -    Book: Física - Uma Abordagem Estratégica - 2ª Edição - Ed. Bookman - 2009.

In Figure 71-08.1 a force F = 1.94 x 10 ^-4N, represented on the charge of - 1 nC. Determine the nature of the charge q and its value, as well as the value of the force attraction or repulsion on the negative charge.

Problem 71-9    Source:  Problem 75 - page 817 - KNIGHT, Randall D. -    Book: Física - Uma Abordagem Estratégica - 2ª Edição - Ed. Bookman - 2009.

The identical small spheres shown in Figure 71-09.1 are loaded with +100 nC and -100 nC. They are suspended, as shown, in the presence of a module electric field equal to 100,000 N/C. What is the mass of each sphere?

Problem 71-10    Source:  Proof 1 - IFSC - SC - 2011.

An electric pendulum of length R and mass m = 2 Kg electrified with a positive charge Q , is repelled by another equal charge, fixed at point A. Figure 71-10.1 shows the equilibrium position of the pendulum. Considering g = 10 m/s² , find the charges module.

Problem 71-11    Source:  Entrance Exam PUCRJ - RJ - 2009.

Two identical spheres, charged with charges Q = 30 µC, are suspended from from the same point by two insulating wires of the same length as shown in Figure 71-11.1. In balance, the angle formed by the two insulating wires with the vertical is 45°. Knowing that the mass of each sphere is m = 1 Kg and considering the Coulomb constant K = 9 x 10⁹ N m²/C², determine the distance between the two spheres when in balance. Consider g = 10 m/s².

Problem 71-12    Source:  Example 16-7 - page 488 - Giancoli - Book: Physics - 5ª edição.

Two point charges are separated by 10 cm. If Q₁ = - 25 µC and Q₂ = + 50 µC, as shown by Figura 71-12.1, determine:

a) the direction and strength of the resulting electric field at the point P located between the two charges and 2 cm from the negative charge.

b) if an electron is placed at rest at point P, what will be its initial acceleration and direction?

Problem 71-13    Source:  Problem elabored by the author of the site.

Being Q₁ = - 50 µC and Q₂ = + 50 µC, find the electric field at points A and B. Use the distances shown in the Figura 71-13.1.