A charge of 8 pC is uniformly distributed throughout the volume between concentric spherical surfaces having radii of 2 cm and 4 cm. What is the magnitude of the electric field 3.2 cm from the center of the surfaces? The value of Coulomb’s constant is 8.98755 × 109 N · m 2 /C 2 . 1. 30.1222 2. 31.0552 3. 18.7438 4. 6.83821 5. 5.14411 6. 11.4753 7. 22.8488 8. 6.46042 9. 54.7116 10. 27.1239 Answer in units of N/C.

Consider the growth of a 20-nm-diameter silicon nanowire onto a silicon wafer. the temperature of the wafer surface is maintained at 2400 k. assume the thermal conductivity of the silicon nanowire is 20 wm-1k-1 and all its surfaces including the tip are subjected to convection heat transfer with the coefficient h = 1×105 wm-2k-1 and t∞ = 8000 k. when the nanowire grows to l = 300 nm, what is the temperature of the nanowire tip (t (x =