Electric Potential

In air, point charges are placed at the four corners of a square with side length $a$. Their charges are $q$, $2q$, $3q$, and $-4q$, respectively.

A ring of radius $R$ has a total charge $q$ distributed uniformly over it.

Two point charges, $q_1 = +3 \times 10^{-7}$ C and $q_2 = -2 \times 10^{-7}$ C, are separated by 5 cm.

When a point charge is moved from point M with a potential of 500 V to point N with a potential of 200 V, the electric field does $-6.0 \times 10^{-5}$ J of work.

The potential difference $U_{AB}$ between points A and B in an electric field is -150 V. A test charge of $q = -3 \times 10^{-6}$ C is moved from point B to point A.

When studying the motion of microscopic particles, the electron-volt (eV) is often used as a unit of energy. 1 eV is the potential energy gained or lost by an electron when it moves through a potential difference of 1 V.

In a vacuum, there is a point charge $Q = -1.2 \times 10^{-6}$ C. An electron is initially located 3 cm away from Q, and then moves to a position 4 cm away from Q.

As shown in the figure, there is a uniform electric field between parallel plates A and B, which carry equal and opposite charges in the air. The electric field strength is $E = 2 \times 10^4$ V/m, and the distance between the plates is 10 cm. In the electric field, point C is 3 cm from plate B, and point D is 2 cm from plate A.

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 $a$.