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A proton is moving to the right in a vertical electric field. A short time later, the proton’s velocity is © 2013 Pearson Education, Inc. Which electric field is responsible for the proton’s trajectory? A. © 2013 Pearson Education, Inc. B. C. D. E. Flux Corresponds to Amount of “fluid mass” Passing Through Area Per Unit Time © 2013 Pearson Education, Inc. The electric flux through the shaded surface is A. 0. B. 200 N m/C. C. 400 N m2/C. D. Flux isn’t defined for an open surface. © 2013 Pearson Education, Inc. The electric flux through the shaded surface is A. 0. B. 400cos20 N m2/C. C. 400cos70 N m2/C. D. 400 N m2/C. E. Some other value. © 2013 Pearson Education, Inc. Which surface, A or B, has the larger electric flux? A. Surface A has more flux. B. Surface B has more flux. C. The fluxes are equal. D. It’s impossible to say without knowing more about the electric field. © 2013 Pearson Education, Inc. Surfaces A and B have the same shape and the same area. Which has the larger electric flux? A. Surface A has more flux. B. Surface B has more flux. C. The fluxes are equal. D. It’s impossible to say without knowing more about the electric field. © 2013 Pearson Education, Inc. Assigning Normal Area Vectors to Small Patches of Closed Surface © 2013 Pearson Education, Inc. Quick Proof of Gauss's Law © 2013 Pearson Education, Inc. These are cross sections of 3D closed surfaces. The top and bottom surfaces, which are flat, are in front of and behind the screen. The electric field is everywhere parallel to the screen. Which closed surface or surfaces have zero electric flux? A. B. C. D. E. Surface A. Surface B. Surface C. Surfaces B and C . All three surfaces. © 2013 Pearson Education, Inc. The electric field is constant over each face of the box. The box contains A. Positive charge. B. Negative charge. C. No net charge. D. Not enough information to tell. © 2013 Pearson Education, Inc. Slide 27-69 Which spherical Gaussian surface has the larger electric flux? A. Surface A. B. Surface B. C. They have the same flux. D. Not enough information to tell. © 2013 Pearson Education, Inc. Spherical Gaussian surfaces of equal radius R surround two spheres of equal charge Q. Which Gaussian surface has the larger electric field? A. Surface A. B. Surface B. C. They have the same electric field. D. Not enough information to tell. © 2013 Pearson Education, Inc. A spherical Gaussian surface surrounds an electric dipole. The net enclosed charge is zero. Which is true? A. The electric field is zero everywhere on the Gaussian surface. B. The electric field is not zero everywhere on the Gaussian surface. C. Whether or not the field is zero on the surface depends on where the dipole is inside the sphere. © 2013 Pearson Education, Inc. A spherical Gaussian surface surrounds an electric dipole. The net enclosed charge is zero. Which is true? A. The electric field is zero everywhere on the Gaussian surface. B. The electric field is not zero everywhere on the Gaussian surface. C. Whether or not the field is zero on the surface depends on where the dipole is inside the sphere. The flux is zero, but that doesn’t require the field to be zero. © 2013 Pearson Education, Inc. Slide 27-78 The electric flux is shown through two Gaussian surfaces. In terms of q, what are charges q1 and q2? A. q1 = 2q; q2 = q. B. q1 = q; q2 = 2q. C. q1 = 2q; q2 = –q. D. q1 = 2q; q2 = –2q. E. q1 = q/2; q2 = q/2. © 2013 Pearson Education, Inc. A cylindrical Gaussian surface surrounds an infinite line of charge. The flux e through the two flat ends of the cylinder is A. 0. B. 2 2rE. C. 2 r2E. D. 2 rLE. E. It will require an integration to find out. © 2013 Pearson Education, Inc. A cylindrical Gaussian surface surrounds an infinite line of charge. The flux e through the wall of the cylinder is A. 0. B. 2rLE C. r2LE. D. rLE. E. It will require an integration to find out. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc.