Integrated Concepts (a) In Figure 18.59, four equal char? ges? q lie on the corners of a square. A fifth ch? arge? q is on a mass m directly above the center of the square, at a height equal to the length d of one side of the square. Determine the magni?tude of? q in te? rms of? q , m , and d , if the Coulomb force is to equal the weight of m . (b) Is this equilibrium stable or unstable? Discuss.

Solution : Step 1 (a) In the figure 18.59 four equal c arges q lie on the corners of a square, A fift h charge q is ona mass m directly above the center of the square, The height equal to the length d of one side of the square, The ma nitude of q i terms of q , m , and d , Hence the coulomb’s force is equal to weight for m. The charges repel each other and unlike charges attract each other. The force of attraction or repulsion between two charges is given by coulomb’s electrostatic law, We need to calculate the charge q kq q F =ab ra2 b, Here, q aq bs magnitude of two charges, k is constant and r is distance between charges.