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*Just tell what farmula to use to solve these type of questions, no need to solv

ID: 2018209 • Letter: #

Question

*Just tell what farmula to use to solve these type of questions, no need to solve the numbers. Thanks!
1. 10 C of charge are placed on a spherical conducting shell. A -3 C-point charge is placed at the center of the cavity. The net charge in coulombs on the outer surface of the shell is?

2. A 5.5x10-6 C charge is 3.5 cm from a -2.3x10-8 C charge. The potential energy of this two-charge system, relative to the potential energy at infinite separation, is?

3. A 5.0-coulomb charge is 10 m from a -2.0-coulomb charge. The electrostatic force on the positive charge is?

4. A parallel-plate capacitor has a plate area of 0.2 m2 and a plate separation of 0.1 mm. If the charge on each plate has a magnitude of 4x10-6 C the electric field between the plates is approximately:

Explanation / Answer

(2). Potential energy of the system U = Kqq' / r where K = coulomb's constant = 8.99 * 10 ^ 9 Nm^ 2/ C^ 2       q ,q' = charges           r = separation (3). electrostatic force F = Kqq/ r^ 2 (4). Capacitance C = A / d where = permitivity of free space = 8.85 * 10 ^-12 C^ 2/ Nm^ 2           A= Area          d = separation charge q = 4 * 10 ^-6 C Potential difference between the plates V = q / C                                                                = qd / A electric field E = V / d                        = q / A (1). charge on shell q = 10 C charge at the center of the cavity q ' = -3 C charge on inner surface of the shell = -q ' = 3 C induced charge due to this innner charge on uoter surface = q ' = -3C So, the net charge on the outer surface of the shell Q = q +(q') = 7 C charge at the center of the cavity q ' = -3 C charge on inner surface of the shell = -q ' = 3 C induced charge due to this innner charge on uoter surface = q ' = -3C So, the net charge on the outer surface of the shell Q = q +(q') = 7 C