Một ống dây thẳng có đường kính D = 5 cm, hệ số tự cảm L = 10 mH được quấn bởi loại dây dẫn có đường kính d = 0,5 mm, các vòng dây được quấn sát nhau và có k = 2 lớp. a) Tìm số vòng dây quấn.
b) Tìm cường độ dòng điện chạy qua dây để mật độ năng lượng từ trường trong ống dây bằng w =

Determine the amount of work done when a crane lifts a 100-n block form 2m above the ground to 6m above the ground

Acave rescue team lifts an injured spelunker directly upward and out of a sinkhole by means of a motor-driven cable. the lift is performed in three stages, each requiring a vertical distance of 10.0 m: (a) the initially stationary spelunker is accelerated to a speed of 4.90 m/s; (b) he is then lifted at the constant speed of 4.90 m/s; (c) finally he is decelerated to zero speed. how much work is done on the 68.0 kg rescue by the force lifting him during each stage?

The temperature at a point (x, y) is t(x, y), measured in degrees celsius. a bug crawls so that its position after t seconds is given by x = 6 + t , y = 8 + 1 3 t, where x and y are measured in centimeters. the temperature function satisfies tx(3, 9) = 5 and ty(3, 9) = 4. how fast is the temperature rising on the bug's path after 3 seconds? (round your answer to two decimal places.)