We have two noise generators: one gives 3 the other 4 V effective voltage. We form a new generator by connecting them in serial arrangement. Then the resultant voltage is 7V. How will this voltage change when we reverse the 4 V generator's polarity?

Two charged particles, q1 and q2, are located on the x-axis, with q1 at the origin and q2 initially at x1 = 12.2 mm. in this configuration, q1 exerts a repulsive force of 2.62 µn on q2. particle q2 is then moved to x2 = 18.0 mm. what is the force (magnitude and direction) that q2 exerts on q1 at this new location? (give the magnitude in µn.)