How to use the change of voltage and current to calculate resistance and electric power

How to use the change of voltage and current to calculate resistance and electric power

The same resistance current is proportional to the voltage, and the ratio is the resistance value, so the ratio of the variation of voltage and current is also the resistance
The change of voltage and current can't calculate the electric power and the change of electric power, unless there are other conditions, we must be careful in the exam
Wheatstone bridge experiment can measure resistance.
R = u variable / I variable (U variable = u large - U small, I variable = I large - I small)
The electromotive rate and its variation should be calculated according to the actual situation, which only tells the variation of current and voltage.
What is the formula for the base area of a triangle
Type it in Chinese characters instead of symbols. I asked about the bottom area, not the area
S = 1 / 2 ah, which is half of the height of the bottom
Let the sum of the first n terms of the arithmetic sequence {an} be SN. It is known that S12 > 0, S13
Let the tolerance be d
S12=(a3+a10)*6=(2a3+7d)*6=(24+7d)*6>0
S13 = A7 * 13 = (A3 + 4D) * 13 = (12 + 4D) * 130 and 12 + 4D
a3=a1+2d=12
a1=12-2d
s12=12a1+66d=144+42d>0
s13=13a1+78d=156+52d
Can resistance and current be calculated with known voltage and power?
Whether the resistance and current can be obtained by knowing the voltage and power,
For example, 220 V, 40 W,
I don't know if time t can be calculated,
Formula P = UI
Current I = P / u i = 40W / 220V = 0.18a
Resistance R = u / I r = 220V /. 18a = 1222 Ω
The voltage and power that the appliance tells you is the rated index. That is to say, if the current voltage is just 220 V, then the power consumption of the appliance is 40 W, and the current is: according to the power formula: P = UI, I = = 220 / 40, then Ohm's law will get the resistance R = u / I, and the deformation formula will not be mentioned. These two are enough!
S is used to represent the area of the triangle, a and H are used to represent the bottom and height respectively, and the formula for calculating the area of the triangle is______ .
Because triangle area = bottom × height △ 2, so s = ah △ 2; so the answer is: S = ah △ 2
Let the sum of the first n terms of the arithmetic sequence {an} be Sn, A3 = 12, S12 > 0, S130, S13
（1）S12=12a1+12×(12-1)／2•d＞0,
S13=13a1+13×(13-1)／2•d＜0
2a1+11d＞0①
a1+6d＜0②
A3 = 12, A1 = 12-2d, ③,
Substituting formula (3) for formula (1) and formula (2),
24+7d＞0
3+d＜0
∴-24／7＜d＜-3．
(2) According to d < 0, A1 > A2 > A3 ＞ ＞a12＞a13．
Therefore, if there is a natural number N in 1 ≤ n ≤ 12,
an＞0,an+1＜0,
SN is the maximum of S1, S2, S12
S12＞0 S13＜0
a1+5d＞-d／2＞0 a1+6d＜0
a6＞0 a7＜0
So in S1, S2 The value of S6 in S12 is the highest
The physical relationship between current, resistance, voltage, power and energy
To format all I=
U=
P=
W=
R=
Please refer to a question I answered a long time ago
What is the formula for calculating the bottom of a triangle
Area * 2 divided by height
In the arithmetic sequence {an}, a = 30, S14 > 0, S13
S14>0,S130
S13=13*a7
wrote it wrong
What are the changes of resistance voltage, electric power and electric power when the current increases? Is there any difference between parallel connection and series connection?
If the equivalent resistance remains unchanged and the voltage increases, the electric power depends on the time and the electric power increases. If the resistance remains unchanged and the voltage remains unchanged in parallel, the current will not change, so the state of the circuit depends on whether the voltage changes
In addition, it is the voltage change that causes the current change, and the current changes passively. It can not be said that the current change causes the voltage change