def moving_charge(self):
    numb_charges = 4
    possible_points = [v.get_start() for v in self.field]
    points = random.sample(possible_points, numb_charges)
    particles = VGroup(*[self.Positron().move_to(point) for point in points])
    for particle in particles:
        particle.velocity = np.array((0, 0, 0))
    self.play(FadeIn(particles))
    self.moving_particles = particles
    self.add_foreground_mobjects(self.moving_particles)
    self.always_continually_update = True
    self.wait(10)
def moving_charge(self):
    numb_charges = 4
    possible_points = [v.get_start() for v in self.field]
    points = random.sample(possible_points, numb_charges)
    particles = VGroup(*[self.Positron().move_to(point) for point in points])
    for particle in particles:
        particle.velocity = np.array((0, 0, 0))
    self.play(FadeIn(particles))
    self.moving_particles = particles
    self.add_foreground_mobjects(self.moving_particles)
    self.always_continually_update = True
    self.wait(10)