问题 选择题

如图8所示,通过水平绝缘传送带输送完全相同的铜线圈,线圈等距离排列,且与传送带以相同的速度匀速运动.为了检测出个别未闭合的不合格线圈,让传送带通过一固定匀强磁场区域,磁场方向垂直于传送带,根据穿过磁场后线圈间的距离,就能够检测出不合格线圈,通过观察图形,判断下列说法正确的是(  )

A.若线圈闭合,进入磁场时,线圈相对传送带向后滑动

B.若线圈不闭合,进入磁场时,线圈相对传送带向后滑动

C.从图中可以看出,第3个线圈是不合格线圈

D.从图中可以看出,第4个线圈是不合格线圈

答案

A、C

若未闭合,则线圈中无感应电流,运动情况不变,即与皮带保持相对静止,即线圈之间的距离保持不变。线圈闭合,则在进、出磁场时会受到安培力的阻碍作用,线圈就会与皮带发生相对运动

阅读理解

SANTO DOMINGO, Domincan Republic ---An infant girl born with a second head bled to death Saturday after complex surgery (外科手术) to remove her partially formed twin , her parents and doctors said.

A medical team completed the 11- hour operation Friday night and said 8-week-old Rebecca Martinez died seven hours later. Doctors had warned after the surgery that the girl would be at great risk of death.

“ We knew this was a very risky surgery , and now we accept what God has decided , “ Rebecca’s father , 29-year-old Frankin Martinez, said at a news conference with his wife. “ Rebecca is no longer with us physically , but no one will forget her.”

Martinez said the family would bury Rebecca in a private funeral later in the day.

The girl lost a lot of blood in the operation, which apparently ( 明显地) caused her to suffer a heart attack , said Dr. Jorge Lazareff , the lead surgeon . Friends and family donated (捐赠) almost 4 gallons of blood for surgeons to use Rebeca’s operation

“This was not a failure or an error ,” Lazareff said . “ When we left here last night the girl was in stable condition. At some point in the middle of the night , she started to bleed.”

Rebecca was born Dec. 10 with the undeveloped head of her twin, an exteremely rare condition known as craniopagus parasticus . Rebecca was the eighth documented case in the world of craniopagus parasiticus, doctors said.

All the other infants documented to have had the condition died before birth , making Rebecca\s surgery the first known operation of its kind.

Without an operation , Rebecca would have barely been able to lift her head at 3 months old. Her doctors said the pressure from the second head would have prevented her brain from developing.

“ We always saw Rebecca without the extra part of her body, ”er father said after her death.

Rebecca was their third child-----along with a 4-year-old boy and a 1-year-old girl.

小题1:The underlined word “infant “ most probably means____________________.

A.a disabled child

B.a newly-born child

C.a 2-headed child

D.a very young child小题2: Rebecca Martinez died ________________________after she went to the operation table.

A.8 weeks

B.11 hours

C.7 hours

D.18 hours小题3: Which of the following statements is NOT true according to the text?

A.Rebecca died because mistakes happened during the operation

B.Rebecca most probably died of bleeding

C.Rebecca was her parents’ third child

D.Without an operation , Rebecca would have little hope of living小题4: Which of the following would be the best title of the passage?

A.Infant Girl Dies After 2nd Head Removed

B.Rebecca , Hiciano’s Third Child

C.The Death of a Gril With two Heads

D.Rebecca’s Surgery, the First Known Operation

单项选择题