题干

如图所示的电路中,电源电压保持不变,已知灯L、电阻R出现了故障,闭合电键S后

①若发现灯L发光,则三个电表中电表示数一定等于零的是____表;

②若有一个电表的示数没有发生变化,则故障可能是____(写出所有可能故障)

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答案(点此获取答案解析)

V1,灯泡L断路了或电阻R短路

同类题2

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为余选项。

    There are some injuries that are common to all types of extreme sports. The following are some of the important things to do to prevent extreme sports injuries. ____ But they can definitely minimize the risk of injuries.

    Warm up.

    ____ They include a combination of cardiovascular(心脏血管的)exercises, strength drills and stretching. Cardiovascular exercises increase body temperature, heart rate and blood circulation, which is required for further movement of the body. Strength drills increase the stamina of the body, while stretching warms up the muscles preparing them for sudden forceful movements. ____ It also plays an important role in boosting the team spirit for a team sport. A warm-up session should last for at least 20 minutes and it can extend up to half an hour.

    Avoid overworking.

    There are some people who do not exercise their body for the sport on a regular basis and perform a week's task in a day or two. ____ They do not realize the effect of overworking during the performance and keep doing it until they feel extremely tired. Apart from the actual sport, one should also avoid overdoing the warm-up exercises before the activity.

    ____

    Just as warming up is essential before any rigorous(充满活力的) physical activity, cooling down the body after playing a rigorous sport is also a significant part of physical conditioning. When you are done with your sports session, you can conclude with some walking, jogging or light running. Slight stretching exercises, focusing on specific muscles, will also be useful for cooling down the body.

A. Cool yourself down.

B. Look for a coach to train you.

C. These people are likely to suffer from extreme sport injuries.

D. However, there are no perfect methods which can assure you 100% safety.

E. Along with physical preparation, warming up prepares you mentally to begin a sport.

F. You should also be careful about your clothing selection for warmth and protection.

G. Warm-up exercises are very important before you begin any sports practice.