Electric Field

An amount of $2 \times 10^{10}$ electrons are added to a small object.

A point charge $Q$ is placed in air. The electric field strength at a distance of 0.2 m from $Q$ is 0.5 N/C.

Two point charges in air, $q_1 = +40 \, \mu$C and $q_2 = +100 \, \mu$C, are separated by 7 m. Point P lies on the line connecting the two charges, at a distance of 2 m from $q_1$. (Note: $1 \, \mu\text{C} = 10^{-6}$ C)

A small charged plastic sphere with mass $m = 3.06 \times 10^{-5}$ kg is suspended and stationary in a uniform electric field of strength $E = 6 \times 10^4$ N/C, which is directed vertically downward.

There is a pair of point charges of equal magnitude and opposite sign, $+q$ and $-q$, separated by a distance $l$. A point A is located on the extension of the line connecting them, and a point B is on the perpendicular bisector of this line. The distances from both A and B to the midpoint of the line connecting the charges are $r$.

An electric dipole consists of two point charges, $+q$ and $-q$, separated by a distance $l$. It is placed in a uniform external electric field of magnitude $E$. The axis of the dipole makes an angle $\theta$ with the direction of the electric field, as shown in the figure.

A positive charge $Q$ sits at the origin of the coordinate system. Point $P$ has coordinates $(1, 1)$.

Two small charged balls $A$ and $B$ are suspended from a fixed support by light insulating threads . $Q_A = 2 \times 10^{-8}$ C and $Q_B = -2 \times 10^{-8}$ C; the horizontal distance between the balls is $3$ cm. In the presence of a uniform horizontal external electric field, both balls remain stationary and both suspension threads hang vertically. $A$ is on the left and $B$ is on the right.

In the non-uniform electric field shown in figure, an electron moves from point $a$ to point $b$ along a field line. The electron is subject only to the electric force, and at point $a$ it has velocity $v_1$ directed along the field line. The field lines are more densely packed at $a$ than at $b$, indicating a stronger field at $a$.

A light string of length $l$ is fixed at its upper end. From its lower end hangs a charged small ball of mass $m$. The system is placed in a uniform horizontal electric field of magnitude $E$. At equilibrium, the string makes an angle $\alpha$ with the vertical, with the ball displaced in the direction of the field.