Chapter 21: Q1CP (page 870)
In Figure 21.15 the magnitude of the electric field is , and the field is at an angle of to the outward-going normal. What is the flux on the small rectangle whose dimensions are by ?
Chapter 21: Q1CP (page 870)
In Figure 21.15 the magnitude of the electric field is , and the field is at an angle of to the outward-going normal. What is the flux on the small rectangle whose dimensions are by ?
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Get started for freeExplain why you are safe and unaffected inside a car that is struck by lightning. Also explain why it might not be safe to step out of the car just after the lightning strike, with one foot in the car and one on the ground (Note that it is current that kills;, rather a small current passing through the region of the heart can be fatal.)
Based on its definition as electric flux per unit volume, what are the units of the divergence of electric field.
You may have seen a coaxial cable connected to a television set. As shown in Figure 21.69, a coaxial cable consists of a central copper wire of radius surrounded by a hollow copper tube (typically made of braided copper wire) of inner radius and outer radius . Normally the space between the central wire and the outer tube is filled with an insulator, but in this problem assume for simplicity that this space is filled with air. Assume that no current runs in the cable.
Suppose that a coaxial cable is straight and has a very long length L, and that the central wire carries a charge +Q uniformly distributed along the wire (so that the charge per unit length is +Q/L everywhere along the wire). Also suppose that the outer tube carries a charge -Q uniformly distributed along its length L. The cylindrical symmetry of the situation indicates that the electric field must point radically outward or radically inward. The electric field cannot have any component parallel to the cable. In this problem, draw mathematical Gaussian cylinders of length d (with d much less than the cable length L) and appropriate radius r, centered on the central wire.
(a). Use a mathematical Gaussian cylinder located inside the central wire and another Gaussian cylinder with a radius in the interior of the outer tube to determine the exact amount and location of the charge on the inner and outer conductors. (Hint: What do you know about the electric field in the interior of the two conductors? What do you know about the flux on the ends of your Gaussian cylinders?)
The electric field on a closed surface is due to all the charges in the universe, including the charges outside the closed surface. Explain why the total flux nevertheless proportional only to the charges that are inside the surface, with no apparent influence of the charges outside.
Figure 21.61 shows disk shaped region of radius of 2 cm on which there is a uniform electric field of magnitude 300 V/m at an angle of 300 to the plane of the disk. Assume that points upward in +y direction. Calculate the electric flux on the disk, and include the correct units.
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