The physics concept formula of the second half of the eighth grade The mid-term exam will be held soon. The formula and concept of electric power will be summarized by experts. Thank you

Chapter 4 electric circuit 1. Two kinds of charge of triboelectrification: electrostatic charge type judgment; electroscope structure (P45 diagram); electric quantity (unit: Coulomb C); material microstructure atomic structure (can be compared with the concept of atom in Chemistry); triboelectrification reason (the transfer of extranuclear electrons) 2. Corresponding concepts of electric circuit Current (and direction: positive charge moving direction); power supply; conductor and insulator; series connection and parallel connection; free charge and moving direction in circuit; circuit diagram; path, open circuit and short circuit; common circuit (corridor circuit; refrigerator circuit: Volume I P60 figure 4-18) Judgment of equivalent circuit: first remove the Ammeter / voltmeter (ammeter: short circuit; voltmeter: open circuit) and then make judgment. 1. Definition, unit (unit symbol) and meaning of each physical quantity (I, u, R, P), conversion ammeter, usage method of voltmeter (range and range selection, series and parallel connection, positive and negative pole, whether it can be directly connected to both ends of power supply) and its structure 2. Measurement of resistance (basic method and change); factors affecting resistance; structure and use of sliding rheostat (p94 figure 7-7); use and reading of rheostat box (p95 figure 7-9, 7-10; potentiometer); deformation of sliding rheostat (P101 figure 7-19); 3. Ohm's law and deformation (pay attention to physical meaning) 4. Series and parallel current, voltage and resistance formula (pay attention to the conditions. For example, the power is proportional to the resistance in series, and inversely proportional in parallel; Joule's law is only applicable to pure resistance circuit when calculating power, and it is applicable to all circuits when calculating heat), 5. Electric work - w = uit = UQ; electric energy meter and measuring power with electric energy meter (p130); electric appliance name plate; refrigerator working time coefficient (p130) 6. Electrical calculation: ① draw the equivalent circuit diagram (draw several diagrams for several States); ② find the equivalent relationship and proportional relationship according to the series and parallel connection; ③ solve (pay attention to the value of current, voltage and electric power in the same state)
Thank you!

According to statistics, the total throughput of domestic and foreign trade of a port in the previous year and last year were 33 million tons and 37.6 million tons respectively, of which the throughput of foreign trade and domestic trade last year increased by 10% and 20% respectively compared with the previous year
The target of this year's port domestic and foreign trade throughput is: the total volume is no less than 42 million tons, of which the foreign trade throughput accounts for no less than 60%. It is estimated that this year's domestic trade throughput will increase by 10% compared with last year. In order to achieve the above target, how many million tons should this year's foreign trade throughput increase compared with last year?
(to have a process, the correct answer should be 3.74 million tons)

If the foreign trade throughput in 2005 is x and the domestic trade throughput is 3300-x, then x (1 + 10%) + (3300-x) (1 + 20%) = 3760x = 20 million tons, the foreign trade throughput is 20 million tons, and the domestic trade throughput is 13 million tons. If the foreign trade throughput in 2007 is x and the domestic trade throughput in 2007 is 17.16 million tons, then x / (x + 1716) = 6

1. Using tractor to plough the land, one fourth of the land was ploughed on the first day, 2 hectares more, and the remaining half was ploughed on the second day. If the land is x hectares, how many hectares of land are left uncultivated two days later?
2. Known a > 0, B

1. On the first day, a quarter of X + 2 ha. On the second day, X - (quarter of X + 2) is left with X - (quarter of X + 2) - half [x - (quarter of X + 2)] = 8 / 3x-12

Cut a 2-meter-long cuboid wood into two equal sections, and the sum of its surface area is increased by 28 square decimeters. How many cubic decimeters is the volume of this cuboid wood

Cut into two sections to show two more sections
The cross-sectional area is 28 / 2 = 14 (square decimeter)
So volume = 14 × 20 = 280 (cubic decimeter)

Nine inches plus one inch = one foot
What idiom is it?

Advance by an inch
If you get an inch, you want to get another foot

Factorization of m ^ 3N ^ 2-m ^ 5N ^ 2

m^3n^2-m^5n^2
= m^2n^2（1 -m^2)
=m^2n^2(1+m)(1-m)

If a + B + C + D is four different natural numbers, and ABCD = 1988, Z, then the maximum value of a + B + C + D is (). Today!

1988=2*2*7*71
Different from each other
So one is 1
Such a 2 is multiplied by another number
Obviously, it's the greatest when it's multiplied by 71
So 1988 = 1 * 2 * 7 * 142
A + B + C + D max = 152

6X (square) + X-2 = 0

6x²-3x+4x-2=0
3x(2x-1)+2(2x-1)=0
(3x+2)(2x-1)=0
x=-2/3,x=1/2

Liberation process: x + 5 / 1 + X + 8 / 1 = x + 6 / 1 + X + 7 / 1
Why don't I calculate (x + 5) (x + 8) = (x + 6) (x + 7) to get 40 = 42?

Try it
If (x + 5) (x + 8) = (x + 6) (x + 7), then x ^ 2 + 13X + 40 = x ^ 2 + 13X + 42, then 40 = 42
Oh, it seems that you are right
Let's look at the topic
Or you are wrong. The original question x + 5 / 1 + X + 8 / 1 = x + 6 / 1 + X + 7 / 1 may express this equation
X+（5/1）+X+（8/1）=X+（6/1）+X+（7/1）
Explanation
It is reduced to 2x + 13 = 2x + 13

Let real numbers x, y, m, n satisfy x2 + y2 = 3, M2 + N2 = 1, and find the maximum value of (MX + NY)

Let x = √ 3 cosa y = √ 3 Sina
m=cosb n=sinb
mx+ny=√3（cosacosb+sinasinb）
=√3cos(a-b)
Maximum = √ 3

The physics concept formula of the second half of the eighth grade The mid-term exam will be held soon. The formula and concept of electric power will be summarized by experts. Thank you