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2015年职称英语考试补全短文练习题 Watching Microcurrents Flow We can now watch electricity as it flows through even the tiniest circuits. By scanning the magnetic field generated as electric currents flow through objects, physicists have managed __________ The technology will allow manufacturers to scan microchips for faults, as well as revealing microscopic defects in anything from aircraft to banknotes. Gang Xiao and Ben Schrage at Brown University in Providence, Rhode Island, visualize the current by measuring subtle changes in the magnetic field of an object and __________. Their sensor is adapted from an existing piece of technology that is used to measure large magnetic fields in computer hard drives. We redesigned the magnetic sensor to make it capable of measuring very weak changes in magnetic fields, says Xiao. The resulting device is capable of detecting a current as weak as 10 microamperes, even when the wire is buried deep within a chip, and it shows up features as small as 40 nanometers across. At present, engineers looking for defects in a chip have to peel off the layers and examine the circuits visually; this is one of the obstacles _____ ______. But the new magnetic microscope is sensitive enough to look inside chips and reveal faults such as short circuits, nicks in the wires or electro migrationwhere a dense area of current picks up surrounding atoms and moves them along. It is like watching a river flow, explains Xiao. | 
