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 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 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 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 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 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.

Problem 136: Two capacitors with capacitance of 6 \(\mu F\) and 4 \(\mu F\) are connected in series across a 100 V dc source. If the supply voltage is cut-off and the two capacitors are connected in parallel, what will be the final charge accumulated in the 4 \(\mu F\) capacitor?

Problem 137: A 40 \(\mu F\) capacitor is charged to store 0.2 J of energy. An uncharged 60 \(\mu F\) capacitor is connected in parallel with the first one through a perfectly conducting leads. What is the energy lost due to the work done by the charges in spreading out over the two capacitors?

Problem 143: A coaxial cable has a 10-mm diameter inside conductor and a metallic sheath with an inside diameter of 20 mm. If the insulating medium has a dielectric constant, k = 2, and a permittivity of \(1.113\times10^{-10}\), what is the capacitance between the conductor and the shield per km?

Problem 144: A lead-sheath cable for underground service has a copper conductor (diameter =0.350 inch) surrounded by 0.20-inch wall of rubber insulation. Assuming the dielectric constant of 4.3 for rubber, calculate the capacitance of the cable per mile length.

Two electrons in a vacuum experience a force of \(2 \times 10^{-15}\) N. How far apart are the electrons?

Two equally charged spheres repel each other with a force of 0.1 kg. If their centers are 20 cm apart, find the charge on each.

Two capacitors A and B have capacitances of 50 μF and 30 μF, respectively. When a 230 V, 50 Hz voltage is applied, find the maximum energy stored assuming A and B are connected in series.

A parallel plate capacitor is made of 350 plates, separated by paraffined paper 0.001 cm thick (k = 2.5). The effective size of the plate is 50 cm × 30 cm. What is the capacitance of this capacitor?

Two electrons experience a force of \(3.46 \times 10^{6}\) N. What is the distance between them?

Two electrons in a vacuum experience a force of \(2 \times 10^{-15}\) N. How far apart are the electrons?

Two capacitors of 0.1 μF, 250 V and 0.2 μF, 500 V are connected in series. What is the maximum voltage that can be applied across the combination?