Physics problems, find solutions

Transmission voltage = transmission line voltage drop + user voltage = transmission line resistance * total current of user + user voltage.

When the user's resistance decreases, the current increases according to Ohm's law; At this time, due to the increase of the total current of the transmission line, the voltage drop of the line will increase, and the user voltage will inevitably decrease due to the certain transmission voltage.

However, there is a key point here, that is, the resistance of the general transmission line is very small, the line voltage drop with the current change is very small, and the voltage drop of the general low-voltage transmission line will not be higher than 5%.

Therefore, although the increase of the total user current will cause the user voltage to decrease, the amount of this voltage reduction is very small, and the resulting decrease in the user current is also very small; It is much smaller than the increase in current due to the decrease in resistance;

Therefore, the general trend is still the increase of user current.

To give a rough example:

The transmission voltage is 230V, the original line voltage drop is 10V, the user voltage is 230-10=220V, and the user resistance is 440 ohms. At this time, the user current is 220 440=; When the user resistance becomes 110 ohms, the line voltage drop becomes 15V, the user voltage decreases to 230-15=215V, and the user current is 215 110=. Although it is smaller than the theoretical 2a (220 110 = 2), the total trend current increases.

When the total resistance of the user decreases, the total resistance of the circuit also decreases, and the current increases. The user voltage decreases, because the current increases, the resistance of the transmission line remains unchanged, the voltage increases, the user voltage = transmission voltage - transmission line voltage, so the user voltage decreases; There is no contradiction that the current increases, the power loss increases, the input current increases, and the user's voltage decreases.

Transmission of electricity, power is certain. Power is equal to current multiplied by voltage.

High voltage for power transmission.

When I arrived at the user village, I became the low-voltage use with a transformer. For example, the increase of 220V current and the increase of power loss are for high-voltage transmission, high voltage, low current, p=i*i*r, small heating loss of transmission line, and saving. If the current is large, the power of the transmission line will be lost, and the power of the transformer to the village will be low.

The user's voltage is not clear, I don't know what it means.

The user voltage is not constant, about 220V, which is generally smaller than that;

Not to contradict it, this place is about the total power. For example, as the current increases, the power loss increases, and the output power also increases.

Solution: According to the lever balance condition: power x power arm = resistance x resistance arm 1kg 10N

m = the mass of the scale is.

3 to 4 The upward force provided by the block exactly submerged in water = the gravitational force of A.

The buoyancy of object B is 1 4 of its gravitational force, and the remaining 3 4 is provided by the upward force provided by the wooden block just submerged in water, i.e., 3 4 of the gravitational force of object B = the gravitational force of A.

Can you click the approval at the bottom right?

Haha, very classic question.

When the machine is faulty, it will make abnormal noise, but it is easy to be masked by the noise of the space environment.

The sound wave conduction loss in the solid is small, the metal rod is solid, one end is against the machine to guide the machine sound, through the metal rod smoothly to the ear (at the same time, the end against the ear also weakens the environmental noise into the ear canal), in this case, it is easier to hear the sound of the machine itself, so as to judge whether the machine is in normal working state and the potential fault according to whether there is abnormal noise.

Answer: Because the sound can be transmitted in the solid, and the vibration of the machine will make a sound when it is running, the operation is different, the sound is different, put one end of a metal rod on various parts of the machine, and put the other end close to the ear to listen, so that you can hear the sound of the machine in more detail, so as to judge the operation of the machine

It should be metal that can transmit sound Listen to the sound of the parts of the machine to see if the tone is normal.

LZ is waiting for someone else's, I'm not sure.

Sound waves belong to mechanical waves, and they are also a kind of mechanical energy, and their energy propagation is greatly affected by the density of the medium, so the sound of the machine is clearer and less noisy with a metal rod as the medium.

The metal rod transmits sound in solid, the sound loss is less, and it is clearer that if the machine is not running properly, there will be loose parts, so that you can hear whether the parts are loose or not.

Solids transmit vibrations more strongly than air. Feel the frequency of the machine's turns.

The absence of vibrations, bumps, and friction sounds is normal.

Echo, because an experienced worker knows what the frequency of the echo looks like when the parts of the machine are operating normally, and if the machine is not operating normally, then its sound frequency is different.

Gravity = gravitational force.

ma=gmm (hten r).

a=gm (hten r).

g=gm/r²

Compared to a g = r (h ten r) = 1 2

r (h dec r) = 1 2

r/h=1/（√2-1）

h=（√2-1）r

Two lengths of rope hang the object, so the pulling distance is twice the distance the object rises.

Therefore, the distance traveled by the pull force is two meters.

So the rally power is 500 2 10 100 watts.

Is the efficiency the ratio of effective power to total power, is it 800 1 10 100 80%.

Known: g=800n, t=10s, h=1m

f = 500n, n = 2 roots (obtained from the figure).

Seeking: p,

Solution: s=hn=1 2=2m

W total = FS = 500 x 2 = 1000 J

p=wTotal t=1000 10=100w

W has =gh=800 1=800j

w has w total = 800 1000