Calculation formula of voltage, resistance, electric power, Watt and Joule's law For example, find the resistance formula: r = u / I = U2 (I can't type root 2 on computer) / P = P / I2 (I can't type root 2 on computer)

Calculation formula of voltage, resistance, electric power, Watt and Joule's law For example, find the resistance formula: r = u / I = U2 (I can't type root 2 on computer) / P = P / I2 (I can't type root 2 on computer)

Symbols, units and calculation formulas of commonly used electrical physical quantities
Physical quantity symbol unit
Symbol unit conversion and formula
Quantity of electricity
Current
Voltage
Resistance
Electric energy (work)
Electrical power
Electric heating
The law of series and parallel circuit
\X09 series circuit / X09 parallel circuit
Current = I1 = I2 + =In\x09I=I1 +I2 +… +In
Voltage: U1 + U2 + +Un\x09U=U1 =U2 =… =Un
Resistance = R1 + R2 + +Rn\x09
Electric power +Pn\x09P=P1 +P2 +… +Pn
Regularity
Expand application
Given the area of △ ABC = 2, let the length of one side of this triangle be x, and the height of this side be y. (1) find the analytic expression of the function between Y and X
1/2*XY=2;
Y=4/X
∵xy×½＝2
∴xy＝4
∴y＝4/x
The analytic expression of the function between Y and X is y = 4 / X
In the arithmetic sequence {an}, it is known that A4 = 70, A21 = - 100. (1) find the first term A1 and tolerance D, and write the general term formula. (2) how many terms in {an} belong to the interval [- 18, 18]?
(1) Let the first term A1 and tolerance D of the arithmetic sequence be: a1 + 3D = 70, a1 + 20d = - 100, so A1 = 100, d = - 10, so an = a1 + (n-1) d = - 10N + 110; (2) from the meaning of the problem, we know that an ∈ [- 18, 18], that is - 18 ≤ - 10N + 110 ≤ 18, the solution is 9.2 ≤ n ≤ 12.8, because n is positive integer
When the resistance of a circuit is 0, we know the voltage and calculate its electric power. What is the formula?
First of all, correct the above answer, the basic formula of electric power is p = UI
The heating power is p = RI ^ 2, no heating does not mean no work
First of all, is there no resistance in the whole loop?
As we all know, the power supply also has internal resistance. If we consider this, the formula is still learned in high school
At this time, many formulas are invalid, but p = UI, as the most basic power formula of electricity, still holds
So, superconductivity, what's the current?
Obviously, it has something to do with time!
Superconducting, at a certain voltage, free electrons begin to accelerate, and continue to accelerate, because there is no resistance, theoretically the speed of electrons can be infinite
Well, this power is related to t
Suppose that there are n electrons in the loop, the electron mass is m, and the loop length is L,
Then E = u / L
So the acceleration of the electron is
Ee/m
After time t, the velocity of the electron is
EET / m, the current is the amount of charge per unit area, that is
Nev / L, then the current is
I = nUte^2/L^2
So the power is
P = UI = ntU^2e^2/(mL^2) = nt(Ue/L)^2/m
Note that t in it is the time after no current starts to add U
What about the kinetic energy? Of course, where does it increase the power
We can verify that
After the electrified time t, the acceleration of the electron EE / M moves T, the velocity is EET / m, and the kinetic energy is 0.5 (EET / M) ^ 2 = 0.5 m (uet / ml) ^ 2 = 0.5 (uet / L) ^ 2 / m
The total kinetic energy is also multiplied by n
By drawing the P-T diagram, we can know that the total power at time t should be p (T) * t / 2 (because the P-T diagram is a triangle, similar to the V-T diagram of uniformly accelerating motion)
Substituting into the power formula just deduced, it just coincides with each other, which shows that the power formula we derived is the formula for transforming electric energy into electron kinetic energy
Finally, to sum up, what is the power
P = nt(Ue/L)^2/m
Where n is the number of electrons in the whole loop, t is the time after adding u from current 0, e is the quantity of electrons, l is the total length of the loop, and M is the mass of electrons
If the side length of an equilateral triangle ABC is x and the area is y, then the functional relation of Y with respect to X is:
The ∵ triangle ABC is an equilateral triangle with side length of 1, and BD = CE = AF, AF = x, ≌ △ bed ≌ △ CFE ≌ △ ABC area = 1 × 1 × sin60 ° / 2 = √ 3 / 4 ≌ y = √ 3 / 4 - √ 3x (1-x) / 4=
Given the tolerance d < 0, a1 + A5 = 12, a2a4 = 32, find the general formula of {an}
an=a1+(n-1)d
a1+a5=a1+a1+4d=2a1+4d=12
a1+2d=6,a1=6-2d;
a2*a4=(a1+d)*(a1+3d)=32;
Substituting A1 = 6-2d, we get
(6-2d+d)*(6-2d+3d)=(6-d)*(6+d)=36-d²=32
d²=4,d=-2(d
Because a1 + A5 = 12, A2 + A4 = 12
And A2 * A4 = 32
So A2 = 12-a4
That is 12-a4-a4 = 32
a4=-10
a2=-2
And because A2 = a1 + D = - 2 (1)
a4=a1+3d=-10 (2)
Why voltage times current equals electric power
First of all, we need to know that w = FD, as we all know, the force is multiplied by the distance of action. In time t, there is an electric quantity of Q, and the electron moves from one section to another. Then the force acting on it is f = Eq. and E = u / d. so w = FD = eqd = u / D * QD = UQ. And the definition of power is p = w / T, so for electricity, P = w / T = UQ / T = UI
∵W=UIt
P=W/t=UIt/t=UI
Definition of current: I = DQ / DT
Definition of voltage: v = DW / DQ
Definition: DWP / DT
Classical mechanics P = f * V
Electricity V * I = DW / DQ * DQ / dt = DW / dt = P
It is known that the area of a triangle is 12 square centimeters, the perimeter of the triangle is x centimeters, and the height of this base is y centimeters. (1) find the functional relationship between Y and X
(1) S △ = √ [P (P-A) (P-B) (P-C)] [P = 1 / 2 (a + B + C)] (hailun qinjiushao formula)
(2) S △ = ABC / (4R) (R is the radius of circumcircle)
(3) S △ = [(a + B + C) R] / 2 (R is the radius of the inscribed circle)
I feel that you have made a mistake in your topic. Which one is the highest at the bottom?
Give you three formulas, hope to be useful to you
Sorry, I made a mistake. I'll go back to my research.
It is known that the general term formula of the sequence {an} is an = 8-3n;
[2] The trend of a series is judged
It can be found that an-a (n-1) is a constant value of 3, so it is an arithmetic sequence with a tolerance of 3
Is the change of electric power equal to the change of voltage multiplied by the change of current
No. It's equal to the change of voltage multiplied by current plus the change of current multiplied by voltage