In an equal-arm balance from the early 20th century (Fig. 31.23), an aluminum sheet hangs from one of the arms and passes between the poles of a magnet, causing the oscillations of the balance to decay rapidly. In the absence of such magnetic braking, the oscillation might continue for a long time, and the experimenter would have to wait to take a reading. Why do the oscillations decay? (a) because the aluminum sheet is attracted to the magnet (b) because currents in the aluminum sheet set up a magnetic field that opposes the oscillations (c) because aluminum is paramagnetic
Figure 31.23 (Quick Quiz 31.5) In an old-fashioned equal-arm balance, an aluminum sheet hangs between the poles of a magnet.
Trending nowThis is a popular solution!
Chapter 31 Solutions
Physics for Scientists and Engineers, Technology Update (No access codes included)
- Review. After removing one string while restringing his acoustic guitar, a student is distracted by a video game. His experimentalist roommate notices his inattention and attaches one end of the string, of linear density = 3.00 103 kg/m, to a rigid support. The other end passes over a pulley, a distance, = 64.0 cm from the fixed end, and an object of mass m = 27.2 kg is attached to the hanging end of the string. The roommate places a magnet across the string as shown in Figure P23.19. The magnet does not touch the string, but produces a uniform field of 4.50 mT over a 2.00-cm length of the string and negligible field elsewhere. Strumming the string sets it vibrating vertically at its fundamental (lowest) frequency. The section of the string in the magnetic field moves perpendicular to the field with a uniform amplitude of 1.50 cm. Find (a) the frequency and (b) the amplitude of the emf induced between the ends of the string.arrow_forwardA 0.5m long straight conductor wire placed on the z-axis carries a current of 10A. If B=-r0,1T in the region where the conductor is located, find the amplitude of the force on the conductor.arrow_forwardA circular coil of radius 0.54 m is placed in a time-varying magnetic field B(t) = (6.00 ✕ 10−4) sin[(18.8 ✕ 102 rad/s) t] where B is in teslas. The magnetic field is perpendicular to the plane of the coil. Find the magnitude of the induced electric field in the coil at t = 0.001 s and t = 0.01 s. |E(t = 0.001)| = v/m |E(t = 0.01)| = V/marrow_forward
- An electromagnetic wave propagating in vacuum has the following magnetic field vector:B(z, t) = ¡(2.00 x 10-8 T)cos(kz - wt). What is the electric field vector at z= 0, and t = 0?(A) (6.00 V/m)k (B) (6.00 V/m)j (C) (6.00 V/m)i(D) (3.00 x 108 V/m)i (E) - (3.00 x 108)j (F) None of thesearrow_forwardWhen the Hemholtz distance condition is satisfied the second derivative of the magnetic field with respect to z vanishes or becomes zero at the center ( point P). Show that both d2Bz/dz2 = 0 and d3Bz/dz3 = 0 at point P.arrow_forwardA conducting strip of unknown width is moving at a speed of 0.33 m/s through a uniform magnetic field of 7.3 T. The maximum voltage produced by the Hall effect across the strip is found to be 4.1 mV. What is the width of the strip?arrow_forward
- In a typical speaker, a stiff cone made of plastic or paper pushes air back-and-forth creating pressure waves that we perceive as sound. The force to drive the cone comes from a coil of wire attached to the base of the cone, which, when current passes through it, experiences a magnetic force. The coil of wire is situated between a concentric magnet as shown below, whose field points N to S radially outward everywhere with a field strength is 0.2 T. The coil of wire has a diameter of 5 cm and is composed of 40 turns of wire with a total resistance of 4 Ω. What is the magnitude of the instantaneous force on the cone in N if a 6 V potential is applied across the ends of the coil of wire? Give your answer to 2 significant digits.arrow_forwardWhich pair of the maximum electric and magnetic fields is/are possible for an electromagneticwave traveling in a vacuum. A. 4.5 MV/m 15 mTB. 9.3 MV/m 31 mTC. 0.14 mV/m 4.5 MTD. 0.31 mV/m 0.3 MTarrow_forwardthe answer must be, A. k= 15.7 rad/m T= 0.125s angular frequency= 50.3 rad/s v= 3.2m/s B. y (x,t) = 0.150cos(15.7x-50.3t) give the solutions on how to find that answers, thank youarrow_forward
- The figure shows three situations - A, B, and C - in which an observer and a source of electromagnetic waves are moving along the same line. In each case the source emits a wave that has a frequency of 4.75 x 1014 Hz. The arrows in each situation denote velocity vectors of the observer and the source relative to the ground and have the magnitudes indicated (v or 2v), where the speed v is 1.80 x 106 m/s. What is the observed frequency in situation B?arrow_forwardElectromagnetic radiation from a 5.50 mW laser is concentrated on a 2.50 mm2 area. (a) What is the intensity in W/m2? W/m2 (b) Suppose a 6.00 nC static charge is in the beam. What is the maximum electric force (in N) it experiences? (Enter the magnitude.) N (c) If the static charge moves at 300 m/s, what maximum magnetic force (in N) can it feel? (Enter the magnitude.) Narrow_forward1) The magnetic flux density in a region of free space is given by B = 2xy ax - 3y ay +2z az T. Find the total force on the rectangular loop shown which lies in the plane z = 0 and is bounded by x = 1, x = 2, y = 5, and y = 7, all dimensions in cm. with I=30 A, in anti-clock wise directionarrow_forward
- Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningClassical Dynamics of Particles and SystemsPhysicsISBN:9780534408961Author:Stephen T. Thornton, Jerry B. MarionPublisher:Cengage Learning