Concept explainers
You are in charge of planning a physics magic show for an open house on your campus. You come up with the following plan for one trick. You will place a sphere on a rough inclined plane of angle θ, as shown in Figure P28.31, and it will not roll down the incline. Here is the secret that only you know: The sphere is nonconducting, has a mass of 80.0 g, and a radius 20.0 cm. A flat, compact coil of wire with five turns is wrapped tightly around it, with each turn concentric with the sphere. The sphere is placed on the incline so that the coil is parallel to the plane. You establish a uniform magnetic field of 0.350 T vertically upward in the region of the sphere. (a) What current in the coil do you need to make this trick work? (b) You explain the trick to a friend in confidence and he suggests lowering the angle θ of the plane to make the required current lower. How do you respond?
Figure P28.31
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Chapter 28 Solutions
Physics for Scientists and Engineers
- An old model of a hydrogen atom has the charge +e of the proton uniformly distributed over a sphere of radius a0, with the electron of charge -e and mass m at its center. (a) What would then be the force on the electron if it were displaced from the center by a distance r # a0? (b) What would be the angular frequency of oscillation of the electron about the center of the atom once the electron was released?arrow_forwardpage 175 q 1arrow_forwardAn electric dipole in a uniform horizontal electric field is displaced slightly from its equilibrium position as shown in Figure P22.50, where θ is small. The separation of the charges is 2a, and each of the two particles has mass m. (a) Assuming the dipole is released from this position, show that its angular orientation exhibits simple harmonic motion with a frequency (b) Suppose the masses of the two charged particles in the dipole are not the same even though each particle continues to have charge q. Let the masses of the particles be m1 and m2. Show that the frequency of the oscillation in this case isarrow_forward
- a) Calculate the acceleration in meters per second squared of the electron if the field strength is 2.50 ✕ 104 N/C.arrow_forwardCalculate the capacitance of a spherical air-filled condenser with a radius of 3 cm inner shell and 9 cm radius of outer shell. A) 9 pFB) 7 pFC) 5 pFD) 2 pFE) 4 pFarrow_forwardA potassium chloride molecule (KCl) has a dipole moment of 8.9 1030 Cm. Assume the KCl molecule is in a uniform electric field of 325 N/C. What is the change in the systems potential energy when the molecule rotates a. from = 170 to 180, b. from = 90 to 100, and c. from = 10 to 0?arrow_forward
- A proton circulates in a cyclotron, beginning approximatelyat rest at the center.Whenever it passes through the gap betweendees, the electric potential difference between the dees is 200 V.(a) By how much does its kinetic energy increase with each passagethrough the gap? (b) What is its kinetic energy as it completes100 passes through the gap? Let r100 be the radius of the proton’scircular path as it completes those 100 passes and enters a dee,and let r101 be its next radius, as it enters a dee the next time. (c) Bywhat percentage does the radius increase when it changes fromr100 to r101? That is, what is percentage increase r101 - r100/r100 100%?arrow_forward(a.) A person is placed in a large, hollow, metallic sphere that is insulated from ground. If a large charge is placed on the sphere, will the person be harmed upon touching the inside of the sphere? Justify your answer in details. (b.) The Sun is lower in the sky during the winter than it is during the summer. How does this change affect the flux of sunlight hitting a given area on the surface of the Earth? (c.) Assume you want to increase the maximum operating voltage of a parallel-plate capacitor. Describe how you can do that with a fixed plate separation. (b.) Looking at your solutions in (a.), can you say a system of charges in Figure 1 is an electric dipole? elaborate your answer in details (c.) Use derived equations in (a.) to evaluate Enet, Vnet and Fnet, given that d = 20 cm and Q = 1.602 nC.arrow_forwardIf r=17.8 θ=51.84 theta dot=0.3454 v=9.95 Find ṙarrow_forward
- Often we have distributions of charge for which integrating to find the electric field may not be possible in practice. In such cases, we may be able to get a good approximate solution by dividing the distribution into small but finite particles and taking the vector sum of the contributions of each. To see how this might work, consider a very thin rod of length L = 16 cm with uniform linear charge density = 50.0 nC/m. Estimate the magnitude of the electric field at a point P a distance d = 8.0 cm from the end of the rod by dividing it into n segments of equal length as illustrated in Figure P24.21 for n = 4. Treat each segment as a particle whose distance from point P is measured from its center. Find estimates of EP for n = 1, 2, 4, and 8 segments. FIGURE P24.21arrow_forwardAn electric dipole moment of p = (8.55, -8.54, 3.28) Cm is inside a uniform electric field of E = (3.25, -6.65, 6.48) V/m. a. What is the potential energy of the dipole? b. What is the magnitude of the torque acting on the dipole?arrow_forwarda) How many days are 544320 s? b) The constant k in Coulomb's law (F= k(Q1Q2/r^2) is k=8.988 10° Nm²/ (As)² Write k with the appropriate prefix. c) Write 34.0 mm² as m² in base power form. d) Calculate the weight of a dumbbell with a mass of 5.0 kg e) Convert 140.0 cm/ s to km/ h. I) Determine the mass of a cone made in molybdenum with radius 0.90 dm and height 1.2 dm. g) Sweden's deepest lake, Vättern, is 128 m deep. Determine the bag pressure at this depth.arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning