试题与答案

一台发电机的功率是44kW,用电阻为0.2Ω的导线输送到用户, (1)若用220

题型:问答题

题目:

一台发电机的功率是44kW,用电阻为0.2Ω的导线输送到用户,

(1)若用220V的电压输电,输电线上的电流多大?输电线发热损失的功率是多少?

(2)若用22kV的电压输电,输电线上电流多大?输电线发热损失的功率又是多少?

答案:

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题型:阅读理解

Should we be afraid of sharks(鲨鱼)? Maybe not. New research into the reasons for shark attacks (攻击) suggests that sharks don’t like the way humans taste! In fact, most people who are attacked by the shark are still alive after receiving only one bite (咬). Why is this?

There are many opinions to explain why sharks sometimes attack people. One opinion is that sharks are just curious (好奇的). We know that sharks are the strongest animals in their environment, so they are not afraid of anything. Naturally, that means they are curious when they meet something unusual. Because they don’t have hands or feet., the only way they can find out an object is to bite it! It is thought that sharks sometimes bite humans for this reason, and then swim away.

Scientists also say that sharks would not waste energy trying to eat a human, as we have a lot of bones (骨头). It is hard for a shark to eat us because sharks don’t have hands, and they can’t pull the meat off our bones. Maybe that’s why they only bite us once. Unluckily, one bite from a large shark is serious enough to hurt people greatly!

Another opinion is that sharks attack humans by mistake. Some sharks may sometimes mistake humans for a seal. An example of this is when a shark  attacks a surfer. A surfer lying on a surfboard looks like a seal when seen from below. Sharks like seals because they have thick fat.

Whatever the reason for shark attacks on humans, sharks should be afraid of us. Sadly, we kill almost 40 million of them each year.

小题1:What happens to people attacked by sharks?

A.Most of them because blind.

B.Most of them because of deaf.

C.Most of them died.

D.Most of them are still alive.小题2: How do sharks find out about an unusual object according to the passage?

A.By biting.

B.By smelling.

C.By touching.

D.By killing.小题3:Which sentence about sharks is true?

A.Sharks pull meat off bones when they eat.

B.Sharks might mistake humans for seals.

C.Sharks like to attack surfers because of their thick fat.

D.One bite from a shark is nothing serious.小题4:What would the author write the passage mainly for?

A.To tell surfers to stay away from sharks.

B.To ask people to stop killing sharks.

C.To let us know the reasons for shark attacks on people.

D.To show that humans are much stronger than sharks.

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