04年?=.=...點解我無印象ge...我前日先做完04 =.=...
1a. magnet... coil,,,,,,,commutator etc.
b. Blades turn -->coil inside turn in the magnetic field --> induced voltage -->current flows through the bulbs and lights up
2a. wavelength x frequency = speed
2b. X... energy lost , amplitude is smaller
2ci. speed = 6x10^3,,,total distance travelled: 0.0435m , 乘番 1000,,, 43.5 mm
2cii plot graph 自搞
2ciii. 睇到個graph 就做到,,,
2d. 題目話佢只係用 1個pulse,,,咁照理只有2個 pulse係CRO 度,1個reflected,1個放出去,但呢度有3個pulse, we can conclude that there's a crack inside the wall , the crack reflect the pulse |