Example w = Pt

Example w = Pt

I = u / R (launch: u = IR, r = u / I)
P=W/t=UI=U²/R=I²R
W=Pt=UIt=u²/R*t=I²R*t

On Ohm's law and the overturning formula of electric power,

In series circuit: I always = I ① = I ② = I ③ = =In
U total = u ① + U ② + U ③ + +Un
R total = u total / I = (U1 + U2 + U3 +...) +Un)/I=R1+R2+R3+…… +Rn
In parallel circuit: I always = I1 + I2 + I3 + +In
U total = U1 = U2 = U3 = =Un
R total = u total / I total = u total / (I1 + I2 + I3 +) +In)=1/R1+1/R2+1/R3+…… +1/Rn

Calculation formula of Ohm's law
Ohm's law is that I (current) = V (voltage) / R (resistance)
When the resistance is constant, the voltage is proportional to the current; r = u / I
When the voltage is constant, the resistance is inversely proportional to the current; u = I * r
When the current is constant, the voltage is proportional to the resistance. I = u / R
What is the u in the law above?

U is the sign of physical quantity of voltage
V is the unit symbol of voltage
When we write a formula, we usually write U (voltage), which corresponds to I (current) and R (resistance)
The unit symbol is used only when substituting the numerical value
V (volt, unit of voltage) corresponds to a (ampere, unit of current) and Ω (ohm, unit of resistance)
Therefore, the formula of Ohm's law should be strictly written as follows:
I=U/R

It is known that the intercept on the Y-axis of the image of the first-order function y = (M & # 178; - 4) x + 1-m is opposite to the intercept on the Y-axis of the image of the first-order function y = (M & # 178; - 2) x + M & # 178; - 3, M =? In addition, what is the intercept

1-m+m²-3=0
∴m²-m-2=0
(m-2)(m+1)=0
∴m=2 m=-1
The intercept is the coordinate of the intersection with the coordinate axis
The intercept on the y-axis is the ordinate of the intersection with the y-axis
The intercept on the x-axis is the abscissa of the intersection with the x-axis

What is the math problem 1 × 1 + 2 × 2 + 3 × 3 + ··· + 20 × 20

1×1+2×2+3×3+···+20×20
=20×（20+1）×（2×20+1）÷6
=20×21×41÷6
=2870

There is a two digit number whose ten digit number is less than one digit number by 2, if the two digit number is greater than 20 but less than 40,31)

Let the ten digit number be a, then the one digit number is (a + 2)
20＜10A+A+2＜40
18＜11A＜38
A = 2 or 3
A + 2 gets 4 or 5
So the two digits are 24 or 35

① It is known that the triangle area enclosed by the line y = kx-6 and the two coordinate axes is 9 to calculate K. ② it is known that the delta area enclosed by the line y = 1 / 2x + B and the two coordinate axes is 4 to calculate B
Using the solution of function

The intersection coordinate of y = kx-6 and coordinate axis is (0, - 6) (6 / K, 0) and its area is | (- 6) * (6 / k) * 1 / 2 | = 9, so k = ± 2
The intersection coordinate of y = 1 / 2x + B coordinate axis is (0, b) (- 2b, 0) and its area is | b * (- 2b) * 1 / 2 | = 4, so B = ± 2

Given that the x-axis of the image intersection of quadratic function intersects at (- 1,0) and (5,0), the equation of the symmetry axis of the image is obtained

x=(-1+5)/2=2

Idioms about animals: animal idioms at the beginning of gate

Ye Gong is a person's name

A construction worker uses 2 parts of cement, 3 parts of sand and 5 parts of stone to prepare 15 tons of concrete. How many tons of cement, sand and stone are needed?

Normal conditions should not be enough, because the bulk density of cement, sand and stone is not the same, but if it is a primary school mathematics problem, it is 15 / 10 = 1.5, so they are 2 * 1.5, 3 * 1.5 and 5 * 1.5 respectively