D

VD:

- Khi không khí là chất cách điện: Bình thường khi ta đứng gần ổ điện, ta không bị điện giật. Điều đó chứng tỏ không khí ở điều kiện bình thường là chất cách điện

- Khi không khí là chất dẫn điện: Khỉ các đám mây giông phóng điện xuống đất (hiện tượng sét đánh) thì không khí khi đó là chất dẫn điện

Hiện tượng 1: khi ở độ ẩm cao không khí có thể dẫn điện( ko chắc lắm)

Hiện tượng 2: khi dòng điện quá cao như ở những nhà máy phát điện dòng điện lên tới 5000 V nêu trong trường hợp này không khí dẫn diện

Đáp án: D

Đáp án là D.

\(x\times\dfrac{20}{11}=\dfrac{1}{1}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{11}\\ x\times\dfrac{20}{11}=\dfrac{10}{11}\\ \Rightarrow x=\dfrac{1}{2}\)

Ta có :

=> X x 20/11 = ( 1 - 1/3 ) + ( 1/3 - 1/5 ) + ( 1/5 - 1/7 ) + ( 1/7 - 1/9 ) + ( 1/9 + 1/ 11 )

=> X x 2/11 = 1 - 1/11 = X x 1/11 = 11/11 - 1/11

=> X x 20/11 = 10/11

=> X = 10/11 : 20/11

=> X = 1/2

\(Xx\dfrac{20}{11}=\dfrac{2}{1}-\dfrac{2}{3}+\dfrac{2}{3}-\dfrac{2}{5}+\dfrac{2}{5}-\dfrac{2}{7}+\dfrac{2}{7}-\dfrac{2}{9}+\dfrac{2}{9}-\dfrac{2}{11}\)

\(Xx\dfrac{20}{11}=\dfrac{2}{1}-\dfrac{2}{11}\)

\(Xx\dfrac{20}{11}=\dfrac{20}{11}\)

\(X=\dfrac{20}{11}:\dfrac{20}{11}\)

\(X=1\)

vậy X = 1

My school seems big from the outside, but is really quite small once you get to know it. It is full of beautiful red brick buildings with arches and ivory. It also has a few more contemporary buildings thrown in there, one parularly interesting one looks a cheese grater :) I think my campus is gorgeous. There is a lovely green quad outside of the freshman dorms and when you walk across it on a warm and sunny SoCal day, you will be amazed. And just wait till you see campus on Game Day, it is a swarm of gold and maroon you have never seen before. My mom still talks about her first game day and seeing the crowds of the people who came out to support the Trojans.

desrcibe ms đúng nhé

Iam going to discuss about my secondary school namely ...........It is one the famous and good school, which is located in .............. and takes 1kms from my village.I studied in this school up to my 5th standard and the syllabus taught here is central syllabus. I used to get good ranks and teachers are from kerala state and they are majors in distinct fields.I really enjoyed my schooling with my friends by playing different games in play ground, coco is one of the best Indian games, which we used to play almost every day for one hour except weekends.To conclude, the school is well-established that contain all sort of facilities , which os necessary for school.

Cảm ơn bn

room

hometown

heavy

how

welcome 

1.room 2. hometown 3.heavy 4.how 5.welcome

1 my uncle doesn't live in house. he live in a ...room...of flats

2 what is your h...ometown......?it's Hue

3 please help me carry the bag.it's so ...heavy..

4 ...how... high is Fansipan Mountain?

5.thank you so much for your help.you're ..welcome ..

Normally, when I have free time, I usually play sports, watch tv, surf webs and read books. After learning stressful hours, such activities help me entertain and relax. And playing sport is the free time activity I like best. Firstly, I like to play sport because it is really a healthy activity. You know, sports provide many benefits for our health. It can improve health and help us to be strong. In the addition, sport help us increase in stature and have a excellent body. Secondly, I like sports. I feel as dynamic as possible. Moreover, It makes me full of energy. Lastly, well, It is what I enjoy most when playing sports. That is sports can help us take up the community. We will knows a lot of people having the same interests in playing sports.Trust me, I was acquainting a lot of friends when I play sports. In short, I like to play sport because it provides many benefits for me. And you? What activities do you like best in your free time?