【单选题】对一个含电源的二端网络,用内阻为 50k Ω 的电压表测得它的端口电压为 30V ,用内阻为 100k Ω 的电压表测得的端口电压为50V,则这个网络的戴维南等效电路的参数为 。
【单选题】有一二端网络,用一内阻为【图片】的电压表测得其端电压为45V,若换用一内阻为【图片】的电压表来测,则测得的端电压为30V,则该网络端电压的真实数值为( )。
【判断题】用电压表测电压,电压表显示的是电池端电压而不是电池的电动势,其原因是由于电池的内阻不为零,流经电压表的电流在电池内产生内压降,只有当电池内电流为零时,电池两端电压才等于电动势。
【简答题】计算题:有一个直流有源二端网络,用内电阻 R′ b =50kΩ的电压表测得它两端的电压Uab=100V,用内电阻为R″ b =150kΩ的电压表测得它两端的电压U ab =150V,求这个网络的等效电压源E 0 和R 0 。
【判断题】自然界中生物变异的概率是不确定的,但是基因遗传算法的变异概率可以人为调节。
【简答题】如图1-93所示电路,开路时测得某直流电源端电压为24V,接上外接电阻R后,用电压表测得R两端电压为20V,用电流表测得流经R的电流I=10A,求电阻R及电源内阻Rs。
【单选题】用电压表测电阻的端电压,电压表的内阻()被测电阻时,电阻的端电压几乎不变。
【单选题】用电压表测量高内阻电路端电压,已知电路的端电压为5V,输出等效内阻为100kΩ,若选用的电压表内阻为1MΩ,对应的数字电压表测得的电压为( )。
【单选题】Why was the little boy disappointed?
A.
He couldn’t get a football shirt from Messi.
B.
His family was too poor to buy him a football.
C.
He couldn’t get a football shirt to look like Messi.
D.
His family cannot afford to pay for football lessons.
【单选题】Why was the little boy disappointed?
A.
He couldn’t get a football shirt from Messi.
B.
He couldn’t get a football shirt to look like Messi.
C.
His family was too poor to buy him a football.
D.
His family cannot afford to pay for football lessons.