Concept explainers
A parallel-plate capacitor has a charge Q and plates of area A. What force acts on one plate to attract it toward the other plate? Because the electric field between the plates is E = Q/Aϵ0, you might think the force is F = QE = Q2/Aϵ0. This conclusion is wrong because the field E includes contributions from both plates, and the field created by the positive plate cannot exert any force on the positive plate. Show that the force exerted on each plate is actually F = Q2/2Aϵ0. Suggestion: Let C = ϵ0A/x for an arbitrary plate separation x and note that the work done in separating the two charged plates is
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Principles of Physics: A Calculus-Based Text
- A proton is released from rest at the origin in a uniform electric field in the positive x direction with magnitude 850 N/C. What is the change in the electric potential energy of the protonfield system when the proton travels to x = 2.50 m? (a) 3.40 1016 J (b) 3.40 1016 J (c) 2.50 1016 J (d) 2.50 1016 J (e) 1.60 1019 Jarrow_forwardFour charged particles are at rest at the corners of a square (Fig. P26.14). The net charges are q1 = q2 = +2.65 C and q3 = q4 = 5.15 C. The distance between particle 1 and particle 3 is r13 = 1.75 cm. a. What is the electric potential energy of the four-particle system? b. If the particles are released from rest, what will happen to the system? In particular, what will happen to the systems kinetic energy?arrow_forwardFour charged particles are at rest at the corners of a square (Fig. P26.14). The net charges are q1 = q2 = 2.65 C and q3 = q4 = 5.15 C. The distance between particle 1 and particle 3 is r13 = 1.75 cm. a. What is the electric potential energy of the four-particle system? b. If the particles are released from rest, what will happen to the system? In particular, what will happen to the systems kinetic energy as their separations become infinite? FIGURE P26.14 Problems 14, 15, and 16.arrow_forward
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- A proton is located at the origin, and a second proton is located on the x-axis at x = 6.00 fm (1 fm = 10-15 m). (a) Calculate the electric potential energy associated with this configuration. (b) An alpha particle (charge = 2e, mass = 6.64 1027 kg) is now placed at (x, y) = (3.00, 3.00) fm. Calculate the electric potential energy associated with this configuration. (c) Starting with the three-particle system, find the change in electric potential energy if the alpha particle is allowed to escape to infinity while the two protons remain fixed in place. (Throughout, neglect any radiation effects.) (d) Use conservation of energy to calculate the speed of the alpha particle at infinity. (e) If the two protons are released from rest and the alpha panicle remains fixed, calculate the speed of the protons at infinity.arrow_forwardLightning can be studied with a Van de Graaff generator, which consists of a spherical dome on which charge is continuously deposited by a moving belt. Charge can be added until the electric field at the surface of the dome becomes equal to the dielectric strength of air. Any more charge leaks off in sparks as shown in Figure P25.52. Assume the dome has a diameter of 30.0 cm and is surrounded by dry air with a "breakdown" electric field of 3.00 106 V/m. (a) What is the maximum potential of the dome? (b) What is the maximum charge on the dome?arrow_forwardA point charge of 4.00 nC is located at (0, 1.00) m. What is the x component of the electric field due to the point charge at (4.00, 2.00) m? (a) 1.15 N/C (b) 0.864 N/C (c) 1.44 N/C (d) 1.15 N/C (e) 0.864 N/Carrow_forward
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