Electrostatics

Problem 115: Three equal positive charges of 10 statcoulomb each are located at the vertices of an equilateral triangle of 2 cm leg. What is the magnitude of the force acting on each charge?

Problem 116: Two point charges 10 cm apart exert a force of \(1 \times 10^{-3}\) grams on each other. If the charges are the same value, what is the value of each charge in stat coulomb?

Problem 117: Two electrons in a vacuum experience a force of \(2\times10^{-15}\) N. How far apart are the electrons?

Problem 118: Two point charges of 2 C and a 5 C are 10 meters apart. A third point charge of 6 C is placed between them. At what distance from the 5 C charge must the 6 C charge be placed, in such a way that it will stay in equilibrium?

Problem 119: Two spheres separated from each other by 10 m have charges of 0.001 coulomb and 0.003 coulomb respectively. In between the two spheres is a point of zero electric field. What is the distance from the 0.001 coulomb sphere?

Problem 120: Calculate the magnitude of the electric field at a point that is 30 cm from a point charge \(Q=-3.2\times10^{-6}\,C\).

Problem 121: Two metallic plates separated by 1 cm are connected across a 12 V battery. A certain plastic material is inserted completely filling the space between the plates and the charge on each plate observed to double. What is the dielectric constant of the plastic material?

Problem 122: Calculate the capacitance between two parallel plates each of which is \(100\,\text{cm}^2\) and 2 mm apart in air.

Problem 123: A capacitor has two parallel metal plates measuring 0.45 m square each. The distance between the plates is 1 cm in free air. If a dielectric material whose permittivity is 4 and 5 mm thick is placed in the upper plate, leaving an air gap between the bottom plate and the dielectric, what is the capacitance of the capacitor?

Problem 124: A capacitor is composed of two plates separated by a 3-mm insulation whose dielectric constant is 4. An additional piece of 6-mm insulation is inserted between the plates. What is the dielectric constant of the additional insulation if the capacitance of the capacitor decreases to half as much of its original value?

Problem 125: A parallel-plate capacitor has an equivalent capacitance of 850 pF. The area of each plate is \(6\,\text{cm}^2\) and the thickness of the dielectric is 0.02 cm. If the material used as the dielectric has a constant of 8, how many sections are there in parallel?

Problem 126: A parallel plate capacitor is made of 350 plates, separated by paraffined paper 0.0010 cm thick (k = 2.5). The effective size of the plate is 15 by 30 cm. What is the capacitance of this capacitor?

Problem 127: A capacitor is charged with 0.23 watt-second of energy at a voltage of 48 volts. What is its capacitance?

Problem 128: A 20 \(\mu F\) capacitor is charged by a 12-V battery. What is the stored energy in the capacitor?

Problem 129: A parallel plate capacitor with air between its plate is charged until the potential difference V appears across it. Another capacitor having hard rubber (dielectric constant = 3) between its plates but otherwise identical, is also charged to the same potential difference. If the energy of the first capacitor is W, that of the second is

Problem 130: A capacitor whose plates is 20 cm x 3.0 cm and is separated by a 1.0-mm air gap is connected across a 12-V battery. Determine the charge accumulated on each plate after a long time.

Problem 131: The result of capacitance \(C_1 = 6\) microfarads and \(C_2\) connected in series is 3 microfarads. Capacitor \(C_2\), in microfarads is

Problem 132: The equivalent capacitance of two capacitors in series is \(0.03\,\mu F\) and when connected in parallel, \(0.16\,\mu F\). If the capacitor with the smaller capacitance is replaced with a capacitor whose capacitance is double as much what will be the new equivalent series capacitance of the combination.

Problem 133: Three capacitors of 16, 15 and 12 \(\mu F\), respectively are connected in series. What is the maximum voltage that can be supplied to the combination if the voltage drop across any of the three capacitors must not to exceed 100 V.

Problem 134: Three capacitors of 20, 10 and 15 \(\mu F\) respectively are connected in series across a 100-V supply. Find the voltage across the 10 \(\mu F\) capacitor.