On the ampere loop theorem, how to understand the current surrounded by closed path Is not vertical through also considered surrounded

On the ampere loop theorem, how to understand the current surrounded by closed path Is not vertical through also considered surrounded

Encirclement refers to the current passing through any point inside the closed path, whether vertical or not
Also note that the positive and negative directions of the current can be offset
Hope to help Loushu
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The essence of Ampere's law of loop
What does its essence mean?

Ampere's loop Law:
The line integral of the intensity vector of the magnetic induction field along any closed path is equal to the algebraic sum of the vacuum permeability times the current passing through the area surrounded by the closed path
∮ l b * DL = μ 0 * ∑ I (L is subscript, B and DL are vectors)
If the current and the direction of the circuit constitute a right-handed spiral relationship, take a positive value, otherwise take a negative value

There are two equal forces F1 and F2. When the angle between them is 90 degrees, the resultant force is F. when the angle between them is 120 degrees, the resultant force is ()
A. 2FB. 22FC. 2FD. F

When the included angle is 90 degrees, f = F12 + F22, so F1 = F2 = 22F. When the included angle is 120 degrees, according to the parallelogram rule, we know that the resultant force and the component force are equal, so f = F1 = 22F. So B is correct, a, C and D are wrong. So we choose B

50 (x + 1) = 55 (x-1) to solve the equation

50(X+1)=55(X-1)
10(x+1)=11(x-1)
10x+10=11x-11
11x-10x=10+11
x=21

How to fill in the number 2 5 9 [] 20

A:
Fill in 14
The difference between 2,5,9,14,20 is 3,4,5,6
That is 9 + 5 = 14

A prime number is a two digit number, and the exchange position between the number on its one digit and the number on its ten digit number is still a prime number. So what are the numbers?
There are only eight brackets

There are nine such numbers: 11, 13, 17, 31, 37, 71, 73, 79 and 97

Finding the maximum value of the function f (x) = x ^ 2-x + 1 in the interval [- 3,0]

y=(x-1/2)^2+3/4
When y is 1 / 2, the minimum value is obtained
ymax=f(-3)=9+3+1=13
ymin=f(0)=0-0+1=1

0, 1, 1, 2, 3, 5, (), (), 9

The last number of 0, 1, 1, 2, 3, 5, (8), (13), 21 should be 21 instead of 9. The rule is: 0 + 1 = 11 + 1 = 21 + 2 = 32 + 3 = 53 + 5 = 85 + 8 = 13, that is, the first two numbers add up to the third number

It is known that N and K are natural numbers, and 1 ＜ K ＜ n, if (1 + 2 + 3 +...) +N-k) / (n-1) = 10, and N + k = a, find the value of A

a=n+k=29
S = 1 + 2 +... + n = n (n + 1) / 2, i.e. (S-K) / (n-1) = (n + 2) / 2 + ((k-1) / (n-1)), it is not difficult to see that,
If n is even, = (n + 2) / 2 integer + ((k-1) / (n-1)) decimal, = 10 is impossible
If n is odd, if and only if (k-1) / (n-1) = 1 / 2, that is, k = (n + 1) / 2, it is the middle number of odd, that is, the average number
The average value of the first n continuous natural numbers after K is removed is exactly (n + 1) / 2 is 10
Then (n + 1) / 2 = 10, n = 19, k = 10, a = n + k = 29

It is known that x = 5 is the solution of the equation 9k-x = 2 (x + 6) with respect to X. try to find the solution of the equation KX / 2 + X / 2 = 2K

By substituting x = 5 into the linear equation 9k-x = 2 (x + 6), the equation is obtained
9k-5=2(5+6)
9k=27
k=3
Substituting k = 3 into the equation KX / 2 + X / 2 = 2K, the equation is obtained
3x/2+x/2=6
4x/2=12
x=3