How to get the expression of electric power How to get the expression P = u * I!

There are w = uit and w = Pt in the book, so p = u * I

Five formulas for calculating electric power

p=UI
P=UU/R
P=IIR
P=W/T
P=FV
Mainly depends on the requirements of the topic to choose

Calculation: 1. Relationship between magnetic flux, coil turns and current (mathematical calculation relationship) 2. Calculation formula of generator power (mathematical calculation relationship)

Do you want these formulas to be useful? You don't have to master them when you are studying foreign trade

Five times of a number is 7.6 more than three times of it. What's the number?
To be selected, you need to make a formula and answer it correctly!
After November 16, the answer is invalid!

Let this number be X
5X-3X=7.6
2X=7.6
X=3.8

It is known that α β is the two roots of the equation 2x & # 178; - 2x = 1. Find α + β = α β = α & # 178; + β & # 178; = 1 / α + 1 / β=

2X & # 178; - 2x = 1 to
2x²-2x-1=0
It can be seen from Veda's theorem
α+β=-(-2/2)=1
αβ=-1/2
α²+β²=α²+β²+2αβ-2αβ=(α+β)²-2αβ=1-2x(-1/2)=1+1=2
1/α+1/β=(α+β)/(αβ)=1/(-1/2)=-2

How to use calculator to calculate this kind of mixed operation: (a + b) x (c + D) x (E + F) =?

The general calculation is 69! If it is larger, it will overflow
Programmable calculator, can be programmed to do more complex calculation test
There is no practical value in measuring the operation speed of calculator, and the operation speed of calculator has little influence on the use
As long as the screen, the key is right

How much is r equal if one of R equals one of R 1 plus one of R 2

1 / r = 1 / R1 + 1 / r2 = (R1 + R2) / (r1r2) so r = r1r2 / (R1 + R2)

Given the function f (x) = (- 3x + 1) ^ 9, G (x) = (X-6) ^ 8, if the sum of binomial coefficients in the expansion of F (x) is a, the sum of absolute values of coefficients is B
The sum of the coefficients in the expansion of G (x) is C, and the maximum absolute value of the coefficients in the expansion is D. the value of AC / BD is calculated

Let x = 1 in F (x), then a = f (1) = - 2 ^ 9;
Let x = - 1 in F (x), then B = f (- 1) = 4 ^ 9;
Let x = 1 in G (x), then C = g (1) = - 5 ^ 8 = 5 ^ 8;
According to the calculation, d = 8 * 6 ^ 7
AB/CD=2^27/[（5^8）*（8*6^7）]
I don't count

How to get the expression of electric power How to get the expression P = u * I!