问题 选择题

在如图所示的电路中,电源电压为U,电阻R1=2R2,设通过R1和R2的电流分别为I1和I2,它们消耗的功率分别为P1和P2,则I1:I2和P1:P2分别是(  )

A.1:2  2:1

B.2:1  2:1

C.1:2  1:2

D.2:1  1:2

答案

两电阻并联,它们的电压U相等,

通过它们的电流之比:

I1
I2
=
U
R1
U
R2
=
R2
R1
=
R2
2R2
=
1
2

它们的功率之比:

P1
P2
=
UI1
UI2
=
I1
I2
=
1
2

故选C.

阅读理解

Nowhere else like Alaska can you enjoy a whale exploding out of the water or an eagle pulling a silver fish from the river. Combine these images with high mountains, brilliant icebergs and wonderful meals and you really do have the Best of Alaska! Join us for an unforgettable 7-day holiday to Alaska!

You can have fun here:

JUNEAU: Juneau, the state capital, is rich in culture and scenic beauty. It is here that we start and end our trip.

HAINES: Haines is a small community located along the fjords (峡湾). The natural beauty and expansive wilderness found here have made Haines an important center for adventure in Alaska.

ALASKA INDIAN ARTS: Alaska Indian Arts is a nonprofit corporation devoted to the preservation and continuation of traditional native craft and culture of the Northwest Native Tribes. You can spend a few hours learning carving, playing native beading (珠子) from local artists.

SKAGWAY: Skagway is a lively town, which still reflects its gold rush roots and origins. In Skagway, you may stop at the Klondike Gold Rush National Park Visitor’s Center and ride the White Pass Yukon Route Railway.

GUSTAVUS: Gustavus is the gateway to Glacier Bay National Park. You’ll stay at a comfortable house here for two nights. This will be the base for both the whale-watching excursion (远足) and a full day cruise (巡游) in Glacier Bay.

DATES/ PRICES:

May 16, June 20, July 18, August 15.

7 days --- $3,500, including lodging, all meals, excursions, guides, park fees, sales taxes, and transportation between Juneau, Skagway, Haines, and Gustavus. Not included: Alcohol, personal items, airfare to and from Juneau.

Contact:

E-mail: info@alaskamountainguides.com

Call: 1.800.766.3396

Address: Alaska Mountain Guides& Climbing School

P.O. Box 1081, Haines AK 99827

小题1:Where can you get to know the local history?

A.In Skagway.

B.In Juneau.

C.In Haines.

D.In Gustavus.小题2:You can watch a whale exploding out of the water at ________.

A.the White Pass Yukon

B.the Klondike Gold Rush National Park

C.Gacier Bay National Park

D.the fjords小题3:The text is mainly written to ________.

A.tell people how to visit Alaska

B.explain why Alaska is famous

C.introduce beautiful places in Alaska

D.attract people to visit Alaska

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