已知R1:R2=2:1,则它们( )
A.串联时的电流之比为2:1
B.串联时的功率之比为1:1
C.并联时的电流之比为2:1
D.并联时的电压之比为1:1
A、串联电路中,电流相等,电流之比1:1.不符合题意.
B、串联电路中,
=P1 P2
=I2R1 I2R2
=R1 R2
.不符合题意.2 1
C、并联电路中,
=I1 I2
=U R1 U R2
=R2 R1
.不符合题意.1 2
D、并联电路中,电压相等,电压之比为1:1.符合题意.
故选D.
已知R1:R2=2:1,则它们( )
A.串联时的电流之比为2:1
B.串联时的功率之比为1:1
C.并联时的电流之比为2:1
D.并联时的电压之比为1:1
A、串联电路中,电流相等,电流之比1:1.不符合题意.
B、串联电路中,
=P1 P2
=I2R1 I2R2
=R1 R2
.不符合题意.2 1
C、并联电路中,
=I1 I2
=U R1 U R2
=R2 R1
.不符合题意.1 2
D、并联电路中,电压相等,电压之比为1:1.符合题意.
故选D.
完形填空。 | |||
There are different kinds of trains in the world. Trains can 1 people, animals, and other things. | |||
( )1. A. carry ( )2. A. help ( )3. A. through ( )4. A. full ( )5. A. seas ( )6. A. water ( )7. A. mend ( )8. A. cook ( )9. A. useful ( )10.A. hate | B. take B. expensive B. among B. dirty B. farm B. air B. watch B. eat B. polite B. are afraid of | C. bring C. fast C. during C. free C. ground C. forests C. reach C. find C. bad C. get on well with | D. hold D. empty D. above D. busy D. gardens D. mountains D. build D. pick D. lucky D. enjoy |