I want to ask a question: if in the experiment, the corresponding current value and voltage value have been given, the resistance value can be obtained by Ohm's law If the results are very different each time, what may be the reason? For example, why are the results different when using a fixed circuit diagram to measure the resistance of the same small lamp? The reason why the resistance value changes is that it is always on for measurement. Does the resistance have a certain temperature? Thank you for your reply

Because the bulb used for a long time, the temperature will rise, the change of temperature will change the value of resistance

In physical experiments: should internal connection or external connection be used in the experiment of describing volt ampere characteristic curve of small bulb? Why? Current limiting or voltage dividing?

In the electrical experiment of high school physics, the internal and external connection of voltammetric resistance ammeter depends on the comparison between the resistance to be measured and the internal resistance of ammeter. In order to reduce the partial voltage of current and the shunt of voltmeter and make the measured value accurate, the resistance to be measured is close to the internal connection of voltmeter, that is, the internal connection of large resistance; on the contrary, the internal resistance of ammeter is close to the external connection of small resistance; the current limiting method can not start from 0; the current limiting method can not start from 0; It is necessary to use partial voltage when small resistance cannot be measured

How to choose ammeter and voltage variable sliding rheostat in volt ampere characteristic curve of small bulb

In electrical experiments, such as measuring resistance by volt ampere method, measuring electromotive force and internal resistance of power supply, and measuring the diagram and line of a certain electrical appliance, there are problems of how to choose electrical experimental equipment, how to choose measuring circuit and control circuit

When measuring the resistance of a small bulb by volt ampere method, it is found that the pointer of the voltmeter does not move and the ammeter shows the number after connecting the power supply
A. The filament of the small light bulb is broken
B. The wiring at both ends of the small bulb is loose
C. The wiring of the ammeter is loose
D. Poor contact on voltmeter terminal
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If the a filament is broken, the ammeter will not show the number. If the wiring at both ends of B is loose, it is equivalent to the same result as option A. if the C answer is loose, it is equivalent to the disconnection of the ammeter, it should not show the number

Given the equation x ^ 2 + y ^ 2-4px-4 (2-P) y + 8 = 0 and P is not equal to 1, P belongs to R
(1) 2. Find the orbit of the center of the circle 3. Find the common tangent equation of the circle

(1) , x ^ 2 + y ^ 2-4px-4 (2-P) y + 8 = 0, written as (x ^ 2 + y ^ 2-8y + 8) + (4y-4x) P = 0
Because the fixed point of the circle has nothing to do with P, so 4y-4x = 0, x ^ 2 + y ^ 2-8y + 8 = 0, there is a solution x = y = 2 (if there is no solution, there is no fixed point), and the fixed point (2,2)
(2) The equation of circle can be reduced to (x-2p) ^ 2 + (y + 2p-4) ^ 2 = 8 (p-1) ^ 2
The center of the circle (2P, 4-2p), so the center locus y = 4-x (x is not equal to 2 (because P is not equal to 1))
(3) The vector from the center of the circle to the fixed point = (2-2p, 2p-2) / / (1, - 1), so a normal vector of the common tangent (the common tangent of all circles in the circle system) is (- 1,1), and the common tangent passes through the fixed point (2,2), so the common tangent equation y = X

The linear equation of the common chord of X & # 178; + Y & # 178; - 4x-3y = 0 and circle X & # 178; + Y & # 178; + 3x-y-5 = 0 is

Just subtract two circles directly
That is, X & # 178; + Y & # 178; - 4x-3y - (X & # 178; + Y & # 178; + 3x-y-5) = 0
That is - 7x-2y + 5 = 0
As for the reason, if you want to know, I'm too lazy to type

What is the chord length of a straight line y = X-1 cut by a circle X & # 178; + Y & # 178; = 1

Let the chord length be 2A
Then: A & # 178; = R & # 178; - D & # 178;
Radius r = 1
The distance from the center of the circle (0,0) to the straight line y = X-1 d = | - 1 | / √ 2 = √ 2 / 2
Then: A & # 178; = R & # 178; - D & # 178; = 1 / 2
So, a = √ 2 / 2
Then: chord length is √ 2

If the distance between point a and X axis is 3 and the distance between the origin is 5, then the coordinate of point P is

Two dimensional? (4,3) (- 4,3) (4, - 3) (- 4, - 3)

If the distance from point P (3, a) to the origin is 5, then a=

Distance from point (x, y) to origin d = √ (X & # 178; + Y & # 178;)
So the distance from point P (3, a) to the origin d = √ (3 & # 178; + A & # 178;) = 5
So 3 & # 178; + A & # 178; = 25
a²=16
a=±4
Hello, I'm glad to answer for you. I hope I can help you
If you don't understand this question, you are welcome to ask
I wish you progress in your study!

What is the distance from point P (- 5,12) to the origin______ ．

∵ point P (- 5,12), ∵ the distance from point P to the origin = 52 + 122 = 13