The chart shows data for four heat engines. Heat Engine

W

Х

Y

Z

Th (K)

620

840

900

500

T. (K)

120

100

300

25

Which lists the engines from most efficient to least efficient?

OY, X, W, Z

OZ, W, X, Y

OZ, X, W, Y

OY, W, X, z

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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 =