1
00:00:00,320 --> 00:00:01,880
Hãy bàn về

2
00:00:01,880 --> 00:00:04,130
phân bố Maxwell.

3
00:00:04,130 --> 00:00:05,360
Hình vẽ ở đây

4
00:00:05,360 --> 00:00:07,540
là bức tranh về James Clerk Maxwell.

5
00:00:07,540 --> 00:00:09,140
Tôi rất thích bức tranh này,

6
00:00:09,140 --> 00:00:12,430
Maxwell và người vợ Katherine, 
cùng với chó của họ, tôi đoán vậy.

7
00:00:12,430 --> 00:00:15,800
James Maxwell là một gã khổng lồ 
của vật lý,

8
00:00:15,800 --> 00:00:17,550
ông nổi tiếng với phương trình Maxwell.

9
00:00:17,550 --> 00:00:19,550
Ông cũng là người đặt nền móng cho

10
00:00:19,550 --> 00:00:22,030
máy chụp hình màu.
Maxwell từng trăn trở

11
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"Sự phân bố của

12
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tốc độ lí tưởng của các

13
00:00:26,520 --> 00:00:29,020
phân tử khí là bao nhiêu?"

14
00:00:29,020 --> 00:00:32,420
Người đàn ông ở đây, Ludwig Boltzmann.

15
00:00:32,420 --> 00:00:34,960
Ông được coi là một trong những 
cha đẻ của

16
00:00:34,960 --> 00:00:37,880
cơ học thống kê.

17
00:00:37,880 --> 00:00:41,360
Dù không hợp tác nhưng cả hai đã
cùng tận dụng

18
00:00:41,360 --> 00:00:42,480
phân phối Maxwell

19
00:00:42,480 --> 00:00:44,530
để phát minh ra cùng một phân phối.

20
00:00:44,530 --> 00:00:46,490
Họ cùng trả lời cho câu hỏi, 
"Phân phối

21
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tốc độ của các phân tử khí 
là bao nhiêu?"

22
00:00:50,737 --> 00:00:52,290
Hãy cùng tìm hiểu qua

23
00:00:52,290 --> 00:00:54,100
hoặc làm một thí nghiệm nhỏ.

24
00:00:54,100 --> 00:00:56,900
Tôi có một thùng chứa ở đây.

25
00:00:57,420 --> 00:00:59,240
Đây là thùng chứa.

26
00:00:59,240 --> 00:01:00,880
Nó chứa không khí.

27
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Mà không khí được tạo nên chủ yếu 
bởi khí nitơ.

28
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Hãy coi như nó chỉ chứa khí nitơ

29
00:01:05,350 --> 00:01:06,778
để đơn giản hóa vấn đề.

30
00:01:06,778 --> 00:01:10,844
Tôi sẽ vẽ một vài phân tử nitơ ở đây.

31
00:01:10,844 --> 00:01:13,558
Tôi có một cái nhiệt kế.

32
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Tôi đặt nó vào đây.

33
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Nhiệt kế chỉ

34
00:01:20,320 --> 00:01:23,810
300 Kelvin.

35
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Điều đó nghĩa là gì?

36
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Trong cuộc sống hàng ngày, chúng ta

37
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có khả năng cảm nhận nhiệt độ 
theo bản năng.

38
00:01:31,730 --> 00:01:33,200
Tôi không muốn chạm vào
một vật nóng.

39
00:01:33,200 --> 00:01:34,630
Nó sẽ làm tôi bị bỏng.

40
00:01:34,630 --> 00:01:38,650
Hoặc vật lạnh sẽ làm tôi bị cóng.

41
00:01:38,650 --> 00:01:40,080
Đó là cách mà não bộ của chúng ta

42
00:01:40,080 --> 00:01:42,300
xử lí nhiệt độ.

43
00:01:42,300 --> 00:01:45,760
Nhưng điều gì thực sự xảy ra
ở cấp độ phân tử?

44
00:01:45,760 --> 00:01:47,630
Nhiệt độ, một cách để

45
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nghĩ về nó

46
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chính xác

47
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là nhiệt đ-

48
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Tôi đánh vần sai.

49
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Nhiệt độ tỉ lệ thuận với 
động năng trung bình

50
00:01:59,480 --> 00:02:02,919
của các phân tử trong hệ thống đó.

51
00:02:02,919 --> 00:02:03,900
Tôi sẽ viết nó ra.

52
00:02:03,900 --> 00:02:08,636
Nhiệt độ tỉ lệ thuận với 
động năng trung bình.

53
00:02:08,636 --> 00:02:09,850
Động năng

54
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trung bình

55
00:02:13,110 --> 00:02:15,740


56
00:02:15,740 --> 00:02:16,720
trong hệ thống.

57
00:02:18,010 --> 00:02:19,600
Tôi sẽ viết là động năng trung bình.

58
00:02:19,600 --> 00:02:21,952
Tôi sẽ mô tả chi tiết hơn.

59
00:02:21,952 --> 00:02:25,810
Tôi có hai thùng chứa.

60
00:02:25,810 --> 00:02:27,297
Đây là một thùng.

61
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Úi.

62
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Hai thùng ở đây.

63
00:02:31,480 --> 00:02:33,240
Chúng có cùng số

64
00:02:33,240 --> 00:02:36,060
phân tử khí nitơ

65
00:02:36,060 --> 00:02:37,440
Tôi sẽ vẽ 10 ở đây.

66
00:02:37,440 --> 00:02:38,830
Trong thực tế

67
00:02:38,830 --> 00:02:40,350
con số phân tử lớn hơn rất rất nhiều.

68
00:02:40,350 --> 00:02:45,350
Một, hai, ba, bốn, năm, 
sáu, bảy, tám, chín, mười.

69
00:02:45,648 --> 00:02:50,640
Một, hai, ba, bốn, năm, 
sáu, bảy, tám, chín, mười.

70
00:02:51,030 --> 00:02:52,760
Cho biết

71
00:02:52,760 --> 00:02:55,210
nhiệt độ là 300 Kelvin.

72
00:02:56,440 --> 00:02:58,940
Nhiệt độ của hệ thống này là 300 Kelvin.

73
00:02:58,940 --> 00:03:01,500
Của hệ thống này là 200 Kelvin.

74
00:03:02,040 --> 00:03:05,900
Nếu tôi muốn hình dung về 
chuyển động của các phân tử này

75
00:03:05,900 --> 00:03:07,450
chúng đang di chuyển xung quanh
và va vào nhau,

76
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không chuyển động đồng đều.

77
00:03:10,540 --> 00:03:12,810
Động năng trung bình

78
00:03:12,810 --> 00:03:15,010
của hệ thống sẽ lớn hơn.

79
00:03:15,010 --> 00:03:16,440
Có thể

80
00:03:16,440 --> 00:03:18,965
phân từ này đang chuyển động theo 
hướng kia.

81
00:03:18,965 --> 00:03:20,830
Đó là vận tốc của nó.

82
00:03:20,830 --> 00:03:22,610
Vật này có vận tốc này.

83
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Cái này chuyển động sang phía kia.

84
00:03:23,770 --> 00:03:25,800
Cái này hầu như không di chuyển.

85
00:03:25,800 --> 00:03:28,100
Cái này đang chuyển động rất nhanh
về phía kia.

86
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Cái này di chuyển với vận tốc 
chóng mặt về đằng kia.

87
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Cái này làm thế này.

88
00:03:32,270 --> 00:03:33,416
Cái này làm thế kia.

89
00:03:33,712 --> 00:03:35,130
Cái này làm thế kia.

90
00:03:35,132 --> 00:03:37,200
Nếu bạn muốn so sáng hệ thống này

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hệ thống này, bạn vẫn có thể có
một phân tử

92
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di chuyển rất nhanh.

93
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Có lẽ phân tử này đang

94
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chuyển động nhanh nhất.

95
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Nhìn chung thì các phân tử ở đây

96
00:03:46,840 --> 00:03:48,730
có động năng thấp hơn.

97
00:03:48,730 --> 00:03:50,780
Cái này có thể đang làm thế này.

98
00:03:50,780 --> 00:03:52,750
Tôi sẽ thử vẽ...

99
00:03:52,750 --> 00:03:56,520
Nhìn chung thì chúng có 
động năng nhỏ hơn.

100
00:03:56,520 --> 00:03:58,110
Điều đó không có nghĩa là
tất cả các phân tử

101
00:03:58,110 --> 00:04:00,110
đều chậm hơn tất cả 
các phân tử ở đây

102
00:04:00,110 --> 00:04:02,160
hoặc có động năng thấp hơn tất cả
các phân tử này.

103
00:04:02,160 --> 00:04:06,901
Nhưng nhìn chung chúng có 
động năng nhỏ hơn.

104
00:04:06,901 --> 00:04:08,930
Chúng ta có thể vẽ một phân phối.

105
00:04:08,930 --> 00:04:10,600
Phân phối này là

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phân phối Maxwell.

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00:04:13,382 --> 00:04:15,110
Nếu chúng ta

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Tôi sẽ vẽ một hệ tọa độ.

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00:04:18,850 --> 00:04:23,850
Tôi sẽ vẽ nó.

110
00:04:24,260 --> 00:04:28,160
Nếu tôi đặt tốc độ trên trục này.

111
00:04:28,670 --> 00:04:30,140
Nếu tôi đặt tốc độ.

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Và trên trục này tôi sẽ đặt 
một số phân tử.

113
00:04:33,532 --> 00:04:38,340
Một số phân tử.

114
00:04:38,690 --> 00:04:39,931
Ngay ở đây.

115
00:04:39,931 --> 00:04:43,310
Với hệ thống 
có nhiệt độ là 300 Kelvin

116
00:04:43,310 --> 00:04:46,092
phân phối có thể trông như thế này.

117
00:04:46,092 --> 00:04:47,831
Nó có thể

118
00:04:47,831 --> 00:04:48,910
phân phối...

119
00:04:48,910 --> 00:04:50,340
Tôi sẽ tô nó màu khác.

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Phân phối

121
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sẽ là tất cả các phân tử.

122
00:04:54,840 --> 00:04:59,330
Phân phối có thể trông như thế này.

123
00:04:59,700 --> 00:05:00,890
Như thế này.

124
00:05:00,890 --> 00:05:02,920
Hệ thống này sẽ là phân phối

125
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Maxwell.

126
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Hãy gọi hệ thống này là A.

127
00:05:07,928 --> 00:05:10,428
Hệ thống A, ở ngay đây.

128
00:05:10,428 --> 00:05:14,710
Hệ thống này có nhiệt độ thấp hơn

129
00:05:14,710 --> 00:05:17,238
nghãi là nó có động năng thấp hơn.

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Phân phối của các phân tử của nó...

131
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Cái có khả năng cao nhất...

132
00:05:22,615 --> 00:05:24,710
Bạn có thể có số phân tử lớn nhất

133
00:05:24,710 --> 00:05:25,900
ở tốc độ thấp hơn.

134
00:05:25,900 --> 00:05:27,330
Cho tốc độ như thế này

135
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ở ngay đây.

136
00:05:28,603 --> 00:05:33,600
Phân phối của nó 
có thể trông như thế này.

137
00:05:35,000 --> 00:05:37,010
Nó có thể trông như thế kia.

138
00:05:37,740 --> 00:05:38,980
Tại sao cái này lại...

139
00:05:38,980 --> 00:05:40,310
Bạn có thể thấy nó hợp lí rằng

140
00:05:40,310 --> 00:05:42,020
tốc độ hợp lí nhất

141
00:05:42,020 --> 00:05:45,500
tốc độ mà khi đó tôi 
có được nhiều phân tử nhất

142
00:05:45,500 --> 00:05:48,460
sẽ thấp hơn tốc độ mà khi

143
00:05:48,460 --> 00:05:51,310
tôi có được nhiều phân tử nhất 
ở hệ thống A

144
00:05:51,310 --> 00:05:54,280
vì tôi có, vì trung bình thì

145
00:05:54,280 --> 00:05:56,050
những vật này có động năng thấp hơn.

146
00:05:56,050 --> 00:05:58,235
Tốc độ của chúng sẽ thấp hơn.

147
00:05:58,235 --> 00:06:00,184
Nhưng tại sao đỉnh này lại cao hơn?

148
00:06:00,184 --> 00:06:01,550
Bạn cần nhớ rằng chúng ta đang bàn về

149
00:06:01,550 --> 00:06:03,080
số phân từ bằng nhau.

150
00:06:03,080 --> 00:06:05,350


151
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152
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153
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157
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158
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159
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161
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162
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163
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164
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165
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166
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167
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168
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170
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171
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179
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180
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181
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182
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183
00:07:35,450 --> 00:07:37,870


184
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185
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186
00:07:41,400 --> 00:07:43,070


187
00:07:43,630 --> 00:07:45,990


188
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189
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190
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191
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192
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193
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194
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195
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196
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197
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198
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199
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200
00:08:20,340 --> 00:08:22,300


201
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202
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203
00:08:26,280 --> 00:08:27,860


204
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