What is the effect of commutator on DC motor 1. Components 2. Working principle 3. What happens if you don't install it four

What is the effect of commutator on DC motor 1. Components 2. Working principle 3. What happens if you don't install it four

1. Each group of windings has at least one pair of contact pieces. If it is a multi winding motor, it is possible for multiple windings to share one contact piece. There is a contact piece connected with the winding, and then there is a carbon brush on the top. 2. The carbon brush does not move due to the continuous movement of the rotor, so that when a group of coils of the rotor are now connected with the carbon brush to form a loop

(2a-3b) (3b-2a) + (a-b) (- A + b) (using multiplication formula) please

The original formula = - (2a-3b) - (a-b) = - (4a-12ab + 9b + a-2ab + b) = - (5a-14ab + 10b)

If the number of equilateral triangles with two vertices on the parabola y2 = 2px (P > 0) and the other vertex as the focus of the parabola is n, then ()
A. n=0B. n=1C. n=2D. n≥3

If one vertex of the equilateral triangle is located in the focus of the parabola y2 = 2px (P > 0), and the other two vertices are on the parabola, then the slope of the two sides of the equilateral triangle about the x-axis is k = ± tan30 ° = ± 33, and the equation is y = ± 33 (x-p2). Each line has two intersections with the parabola, and the two intersections on both sides of the focus are connected So n = 2, so choose C

How much water to add to 500 ml 75% alcohol and 60% alcohol

Alcohol = 500 × 75% = 375 ml
375÷60%=625ml
Add water = 625-500 = 125ml
Do not understand can ask, help please adopt, thank you!

What are the factors of 1980

1 2 3 4 5 6 9 10 12 15 18 20 22 30 36 44 45 55 66 90 99 110 132 165 198 220 330 396 495 660 990 1980 all of these, without the main reward of the building, it's not easy to play all of them

9. Calculate ∫ (upper and lower limit 0 ~ + ∞) Xe ^ (- x ^ 2) DX=

∫xe^(-x^2)dx|(0,+∞)u=-x^2du=-2xdx∫xe^(-x^2)dx=-(1/2)∫e^udu=-(1/2)e^u+C=-(1/2)e^(-x^2)+C=-1/2e^(x^2)+C∫xe^(-x^2)dx|(0,+∞)=[-1/2e^(+∞^2)+C]-[-1/2e^(0^2)+C]=1/2

The mass of a hollow shot is 27g. The total mass of the hollow part of the shot filled with alcohol is 43g. What is the volume of the shot?

43g-27g = 16g, which is the mass of alcohol
Suppose the density of alcohol is t (g / cm ^ 3), the density of different kinds of alcohol will be different, depending on your situation
Volume = mass / density, its volume is 16 / T (cm ^ 3)

Define a kind of "F" operation on positive integer n. 1. When n is odd
The result is 3N + 5; 2. When n is even, the result is n / 2K (the K power of 2) (where k is a positive integer that makes the original expression odd), and the operation is repeated
26F②→13F①→44F②→11……
If n = 449, the result of the 2013 "f operation" is -——

The first time: 449x3 + 5 = 1352
The second time: "1352 / 8 (the third power of 2) = 169
The third time: 169x3 + 5 = 512
The 4th time: 512 / 512 (the 9th power of 2) = 1
The fifth time: 1x3 + 5 = 8
The 6th time: 8 / 8 = 1
……
In 8 and 1 cycles, the odd number is 8 and the even number is 1
In 2013, it was 8

How to calculate the tangent plane of ellipsoid X & # 178 / A & # 178; + Y & # 178 / / B & # 178; + Z & # 178 / / C & # 178; = 1?

The function f (x, y, y, z) f (f (x, y, y, z) is the function f (x, y, y, z) f (f (x, y, y, z) function f (x, y, y, z) f (f (x, y, y, y, z) f (x, y, y, x, y, y, z) function f (f (x, y, y, y, x, y, x, y, x, y, x, y, x, y (x, x, y = 2x / A / A / b \\\\\\\\\\\\\\\\\\\\\\\\\it's not easy

Several commonly used experimental methods of junior high school physics (such as equivalent substitution method) are best exemplified

1、 The so-called control variable method is that in the process of studying and solving problems, the factors or conditions that affect the changing law of things are artificially controlled to make some of the conditions change or not change according to the specific requirements