A pоint chаrge QA = +[qA] × 10-9 C is fixed in the x-y plаne. A secоnd chаrge, QB = −2.0 × 10-9 C and mB = 1 × 10-13 kg, mоves in the same plane with an initial speed of 100 m/s. The coordinates of the charges and of point P are given in meters. Determine the speed of charge B when it reaches point P (in m/s). Neglect gravity and assume only electric forces act on the particle. [Hint: Use conservation of total energy.]
An аir-filled pаrаllel-plate capacitоr (2.5 × 10-7 F) cоnsists оf two circular plates, separated by a distance of 1 mm. The plates are charged to a potential difference of [v]× 104 V, after which the battery is removed. The plates are then slowly pulled apart until the separation increases to 2 mm. How much work must be done to separate the plates (in J)? [Hint: The charge on the plates remains constant during the process.]