【简答题】三、在图示电路中, 已知 V CC = 12V ,晶体管的 b = 100 , R’ b = 100k Ω 。填空:要求先填文字表达式后填得数。 ( 1 )当 Ui = 0V 时,测得 U BEQ = 0.7V ,若要基极电流 I BQ = 20 μ A , 则 R’ b 和 R W 之和 R b = ≈ k Ω ;而若测得 U CEQ = 6V ,则 R c = ≈ k Ω 。
【简答题】Cathy is taking notes of the grammatical rules in class at Sunshine School, where she __________ English for a year. A.studies B.studied C.is studying D.has been studying
【单选题】根据现行《火灾自动报警系统设计规范》,设备面盘的排列长度大于4m时,其两端应设置宽度不小于()的通道
【单选题】The publication of _____ established Emerson as the most eloquent spokesman of the New England Transcenden- talism.
【单选题】According to the passage, the processing of the new antibiotic and vaccines becomes an engineering problem when ______.
A.
it involves the low-cost production of large quantities
B.
these items originate in the work of biochemistry
C.
people are engaged in safe operations in the test-tube stage
D.
business agents use efficient methods to market these items
【单选题】The publication of ______established Emerson as the most eloquent spokesman of the New England Transcendentalism.
【单选题】关于细菌对氧的需要分类,下列哪项是正确的( )
【单选题】消防控制室内设备的布置,当设备面盘的排列长度大于 m时,其两端设置宽度不小于1m的通道。