Concept explainers
The rank of the emf induced in the coil at the instants marked
Answer to Problem 1OQ
The rank of the emf induced in the coil at the instants marked
Explanation of Solution
Write the expression for induced emf by Faraday’s law.
Here,
The above equation signifies that the induced emf is directly proportional to the negative of flux that is, the induced emf will have a maximum positive value when the flux has a maximum negative value and vice versa.
The induced emf at point
Conclusion:
Therefore, the rank of the emf induced in the coil at the instants marked
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Chapter 31 Solutions
Physics: for Science.. With Modern. -Update (Looseleaf)
- Figure P23.58 is a graph of the induced emf versus time for a coil of N turns rotating with angular speed ω in a uniform magnetic field directed perpendicular to the coil’s axis of rotation. What If? Copy this sketch (on a larger scale) and on the same set of axes show the graph of emf versus t (a) if the number of turns in the coil is doubled, (b) if instead the angular speed is doubled, and (c) if the angular speed is doubled while the number of turns in the coil is halved. Figure P23.58arrow_forwardA bar magnet is held in a vertical orientation above a loop of wire that lies in the horizontal plane as shown in Figure OQ23.13. The south end of the magnet is toward the loop. After the magnet is dropped, what is true of the induced current in the loop as viewed from above? (a) It is clockwise as the magnet falls toward the loop. (b) It is counterclockwise as the magnet falls toward the loop. (c) It is clockwise after the magnet has moved through the loop and moves away from it. (d) It is always clockwise. (e) It is first counterclockwise as the magnet approaches the loop and then clockwise after it has passed through the loop.arrow_forwardA thin copper rod of length L rotates with constant angular velocity about a point O, in a plane perpendicular to a uniform magnetic field B as shown in Figure P32.20. Determine the induced emf across its ends. Consider that the emf produced between the point O and a small segment of the rod, d, is given by d=Bvd.arrow_forward
- 100-turn square coil of side 20.0 cm rotates about a vertical axis at 1.50 103 rev/min as indicated in Figure P31.42. The horizontal component of the Earths magnetic field at the coils location is equal to 2.00 105 T. (a) Calculate the maximum emf induced in the coil by this Held, (b) What is the orientation of the coil with respect to the magnetic field when the maximum emf occurs?arrow_forwardA thin conducting bar (60.0 cm long) aligned in the positive y direction is moving with velocity v=(1.25m/s)i in a region with a spatially uniform 0.400-T magnetic field directed at an angle of 36.0 above the xy plane. a. What is the magnitude of the emf induced along the length of the moving bar? b. Which end of the bar is positively charged?arrow_forwardA time-dependent uniform magnetic field of magnitude B(t) is confined in a cylindrical region of radius R. A conducting rod of length 2D is placed in the region, as shown below. Show that the emf between the ends of the rod is given by dBdtDR2D2 . ( Hint: To find the between the ends, we need to integrate the electric field from one end to the other. To find the electric field, use Faraday’s law as “Ampere’s law for E”.)arrow_forward
- A parallel-plate capacitor with plate separation d is connected to a source of emf that places a time-dependent voltage V(t) across its circular plates of radius r0and area (a) Write an expression for the time rate of change of energy inside the capacitor in terms of V(t) and dV(t)/ dt. (b) Assuming that V(t) is increasing with time, identify the directions of the elecuic field lines inside the capacitor and of the magnetic field lines at the edge of the region between the plates, and then the direction of the Poynting vector S at this location. (c) Obtain expressions for the time dependence of E(t), for B(t) from the displacement current, and for the magnitude of the Poynting vector at the edge of the region between the plates. (d) From S , obtain an expression In terms of ‘(t) and dV(t)/dt for the rate at which electromagnetic field energy the region between the plates. (e) Compare the results of pails (a) and (d) and explain the relationship between them.arrow_forwardAn instrument based on induced emf has been used to measure projectile speeds up to 6 km/s. A small magnet is imbedded in the projectile as shown in Figure P23.2. The projectile passes through two coils separated by a distance d. As the projectile passes through each coil, a pulse of emf is induced in the coil. The time interval between pulses can be measured accurately with an oscilloscope, and thus the speed can be determined. (a) Sketch a graph of V versus t for the arrangement shown. Consider a current that flows counterclockwise as viewed from the starting point of the projectile as positive. On your graph, indicate which pulse is from coil 1 and which is from coil 2. (b) If the pulse separation is 2.40 ms and d = 1.50 m, what is the projectile speed? Figure P23.2arrow_forwardA loop of wire in the shape of a rectangle of width w and length L and a long, straight wire carrying a current I lie on a tabletop as shown in Figure P23.7. (a) Determine the magnetic flux through the loop due to the current I. (b) Suppose the current is changing with time according to I = a + bt, where a and b are constants. Determine the emf that is induced in the loop if b = 10.0 A/s, h = 1.00 cm, w = 10.0 cm, and L = 1.00 m. (c) What is the direction of the induced current in the rectangle? Figure P23.7arrow_forward
- A Figure P32.74 shows an N-turn rectangular coil of length a and width b entering a region of uniform magnetic field of magnitude Bout directed out of the page. The velocity of the coil is constant and is upward in the figure. The total resistance of the coil is R. What are the magnitude and direction of the magnetic force on the coil a. when only a portion of the coil has entered the region with the field, b. when the coil is completely embedded in the field, and c. as the coil begins to exit the region with the field?arrow_forwardA bar magnet is dropped through a loop of wire as shown in Figure P32.64. a. What is the direction of the induced current as the magnet is approaching the loop, as viewed from above where the magnet begins? b. What is the direction of the induced current after the magnet falls through and is receding from the loop, as viewed from above where the magnet began? FIGURE P32.64arrow_forwardA bar magnet is held in a vertical orientation above a loop of wire that lies in the horizontal plane as shown in Figure OQ31.7. The south end of the magnet is toward the loop. After the magnet is dropped, what is true of the induced current in the loop as viewed from above? (a) It is clockwise as the magnet falls toward the loop. (b) It is counterclockwise as the magnet falls toward the loop. (c) It is clockwise after the magnet has moved through the loop and moves away from it. (d) It is always clockwise. (e) It is first counterclockwise as the magnet approaches the loop and then clockwise after it has passed through the loop.arrow_forward
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