Students are testing the ability of a device to prevent the transfer of thermal energy. They conduct the test by placing a container of heated water inside the container. The most useful data for testing the ability of the device to prevent the flow of energy would be which of the following? A. The density, in grams per cubic centimeter, or the materials used to build the device.
B. The volume, in cubic centimeters, of empty space inside the container
C. The volume, in milliliters, of hot water in the container placed inside the device
D. The change in the temperature, in degrees Celsius, of the water over one hour

To understand the behavior of the electric field at the surface of a conductor, and its relationship to surface charge on the conductor. a conductor is placed in an external electrostatic field. the external field is uniform before the conductor is placed within it. the conductor is completely isolated from any source of current or charge. part a: which of the following describes the electric field inside this conductor? it is in the same direction as the original external field.it is in the opposite direction from that of the original external field.it has a direction determined entirely by the charge on its surface.it is always zero. part b: the charge density inside the conductor is: 0non-zero; but uniformnon-zero; non-uniforminfinite part c: assume that at some point just outside the surface of the conductor, the electric field has magnitude e and is directed toward the surface of the conductor. what is the charge density η on the surface of the conductor at that point? express your answer in terms of e and ϵ0