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【单选题】
下列说法中哪个是正确的?( )
A.
系统不受外力作用,则它的机械能和动量都是守恒的.
B.
系统所受的外力矢量和为零,内力都是保守力,则机械能和动量都守恒
C.
系统所受的外力矢量和不为零,内力都是保守力,则机械能和动量都不守恒
D.
系统不受外力的作用,内力都是保守力,则机械能和动量都守恒
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【单选题】We define : V D is the voltagebetween P terminal and N terminal, ID is the current passing through the diode,and it’s direction is from P to N. if >0 and>0, the diode is in the ( ) region
A.
0-bias
B.
forward-bias
C.
reverse-bias
D.
Zener
【单选题】A diode can be usedas a constant-voltage reference in a circuit, the diode is
A.
photodiode
B.
light-emitting diode
C.
Schottky barrier diode
D.
Zener diode
【简答题】用18mol/L的浓硫酸配制80mL 1.0mol/L的稀硫酸,需用的实验仪器有:A.100mL量筒 B.托盘天平 C.玻璃棒 D.50mL容量瓶 E.10mL量筒 F.胶头滴管 G.50mL烧杯 H.100mL容量瓶 (1)实验时应选用仪器的先后顺序是(填入编号)______. (2)在容量瓶的使用方法中,下列操作不正确的是______ (填写标号). A.使用容量瓶前先检查它是否漏水 B.容量...
【单选题】Most modern diodes are based on semiconductor ( ). In a p-n diode, conventional current can flow from the ( ) side (the anode) to the ( ) side (the cathode), but cannot flow in the ( ) direction. ( )
A.
p-n junction, p-type, n-type, opposite
B.
p-n junction, n-type, p-type, opposite
C.
n-p junction, A-type, K-type, opposite
D.
p-n junction, A-type, K-type, opposite
【判断题】亚洲债券市场的发展源于人们对1997年东南亚金融危机的反思。( )
A.
正确
B.
错误
【简答题】实验室需用480mL0.2mol?L -1 的稀硫酸,现用18.4mol?L -1 的浓硫酸来配置. (1)计算所需浓硫酸的体积为______mL. (2)所需仪器除了玻璃棒、烧杯、胶头滴管、量筒外,还需要哪个仪器才能完成该实验,请写出:______. (3)实验中两次用到玻璃棒,其作用分别是:______、______. (4)下列对容量瓶及其使用方法的描述中正确的是______. A.容量瓶上...
【单选题】We define : V D is the voltagebetween P terminal and N terminal, is the current passing through the diode,and it’s direction is from P to N. if the diode is in the reverse-bias region,then ( )
A.
>0, >0
B.
=0, =0
C.
< 0,=- , isreverse saturation current of the diode
【单选题】We define : V D is the voltagebetween P terminal and N terminal, ID is the current passing through the diode,and it’s direction is from P to N. if VD=0 and ID =0, the diode is in the ( ) region
A.
0-bias
B.
forward-bias
C.
reverse-bias
D.
Zener
【简答题】实验室用18.4 mol·L -1 的浓硫酸来配制500mL 0.2 mol·L -1 的稀硫酸。 (1)所需仪器除了玻璃棒、烧杯、胶头滴管、量筒外,还需要哪个仪器才能完成该实验,请写出: 。 (2)计算所需浓硫酸的体积为________ mL 。现有①10mL ②50mL ③100mL三种规格的量筒,应当选用___________。(填序号) (3)实验中两次用到玻璃棒,其作用分别是:_____...
【单选题】Light-emitting diode emit light when the p-n junction is ___________
A.
forward-biased
B.
reverse-biased
C.
zero biased
D.
operating in the Zener region
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