This summer vocation I am going to do a lot of _________ to prepare for the senior high school.
A:job
B:work
C:invention
D:service
如图所示的电路中,电阻R1的阻值为10Ω,电源电压不变.当开关S接1时,电压表的示数为8V,电流表的示数为1.2A.求:
(1)R2的阻值是多少?
(2)当开关S接2时,若通电1min,电阻R2产生的热量是多少?
在献血或输液时,针头插入的血管是( )
有关亚洲的叙述,正确的是( )