checkpoint_01

Checkpoint 01

Forces on Two Charges

• Two Charges [ q = + 1 \mu \text{C} ] and [ Q = +10 \mu \text{C}] are placed near each other as shown in the figure 1) Which of the following diagrams best depicts the forces acting on the charges?
  • C
    • Charge [q] is [frac{ 1}{ 10}] the magnitude of charge [Q] but the charges have an equal and oposite effect on one another. Therefore, the [F_{qQ} = F_{Qq}]

Compare Forces

• Consider the two cases shown below. In both cases a central charge q has two charges of equal magnitude at equal distances above and below it. In Case 1 the signs of the two outer charges is opposite, and in Case 2 they are both positive. You are not told the sign of the charge in the center q. In which Case is the magnitude of the net force on the center charge bigger?
  • Case 1
    • In case2 the force of the two [+Q] charges cancel one another out as the are push the charge equally in opposite directions. In case1 [+Q] is pushing the charge downward and the [-Q] is pulling the charge downward, in turn producing a higher net force on the center charge.

Force from Four Charges

• A positive charge [Q] is placed at the origin. Four other positive charges are placed on a circle in the [x-y] plane centered on [Q] as shown. The top charge is located on the [y] axis and has a magnitude of [3q]. The three bottom charges are symmetric about the y axis as shown and each has magnitude [q].
  • Which of the following statements best describes [F_X], the [x] component of the net force on the charge at the origin?
    • [F_x = 0]
    • The forces along the x-axis sum to zero.
  • For the collection of charges shown in the above problem, which of the following statements best describes [F_Y], the [y] component of the net force on the charge at the origin?
    • [F_Y < 0 ]
    • While all force of the [3q] is directed along the negative [y] axis, some of the force exerted on [Q] by two of the [q] charges is directed along the [x] axis and therefore [F_N] is along the negative [y] axis.