If you are looking for questions about the calculation of power and mechanical efficiency, it is bes

1. In "measuring the resistance of the small bulb" and "measuring the power of the small bulb" (the rated voltage of the small bulb is in the two experiments:

1) Three sets of voltage and current values need to be measured, the purpose of the former is the purpose of the latter

2) The following table is the data recorded by Li Shuo during the experiment of "measuring the power of small bulbs", from which it can be seen that the rated power of small bulbs p = w.

3) When the students were exchanging their experimental experience, some students proposed that the resistance of the small bulb could be calculated under the condition of non-rated voltage according to Li Shuo's measurement data, and then the rated power p of the small bulb could be calculated by the formula', please use this method to calculate the amount of p based on the data in **'(required to have the necessary calculation process), place the p-amount and the p-amount'Compare and analyze the root causes of this discrepancy.

Solution: 1) measure the resistance and electrical power of small bulb with voltmeter and ammeter, the measuring circuit and method are exactly the same, the former uses the resistance of calculating bulb, the latter uses p=iu to calculate the power of bulb, three groups of voltage values and current values are measured in the measurement process, the purpose of the former is to carry out multiple measurements, find the average value of resistance, reduce the error of measurement; The purpose of the latter is to measure the rated power of the small bulb at the rated voltage and the actual power not at the rated voltage, and compare it to find the relationship between the luminous brightness of the small bulb and the actual power and the actual voltage.

2) The rated voltage of the small bulb is, as known from the experimental data, when the voltage at both ends of the bulb is equal to the rated voltage, the current through the bulb is, and the rated power of the small bulb P = IU = .

3) According to the data measured by the experiment, when U1 = 3V, I1 = the resistance of the bulb at this time, the rated power of the small bulb, and the amount of P'p amount, the reason is that the resistance of the filament is affected by temperature, when the voltage is high, the temperature of the filament is high, and the measured resistance is large, and the p amount calculated by can be known'If the value is small, if U3 = 2V and I3 = Calculate the resistance r3, the calculated p amount is determined by'The value will be on the larger side.

Note: This question tests the ability to analyze and process experimental data, summarize and draw experimental conclusions. Through problem solving, deepen the understanding and mastery of the similarities and differences between the bulb resistance and electric power experiments measured by voltmeter and ammeter, and at the same time, it is found that the resistance of the bulb filament increases with the increase of temperature (or the increase of actual electrical power).

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Dig the foot of the wall Kara to make space.

A "220V, 100W" light bulb led from the power supply to a construction site was dim, and the actual power of the bulb was only 81 watts, while the voltage of the power supply was indeed 220 volts. How much power is consumed on a transmission line? What approximations do you use in your calculations?

If the power of the generator is 560,000 kilowatts, the efficiency of the generator to convert mechanical energy into electrical energy is 80%, and the energy loss caused by heat transfer and the friction of the turbine during the passage of water vapor through the turbine are not considered.

1 (1) Mechanical efficiency = w has w total = gh (g + g 0) h = 600n (600n + 40n ) = (2) in the process of lifting the weight by 1 meter, the person does work w = (g + g 0) h = (600n + 40n ) x1m = 640j (3) in the process of lifting the pressure of the person on the ground g -f = 600n - (600n + 40n ) 2 = 280n (4) when the mechanical efficiency is the largest, the pressure of the person on the ground is 0, when the rope pull force =The maximum efficiency is at 600N, and the total upward tension of the rope is 600Nx2=1200N, maximum cargo weight G=1200-40N=1160N, mechanical efficiency=W, there is W, Total=GH (G +G0)H=1160N, 1200N= gravity to be irrigated, G=mg=PVG=PSHG=1000KG, m 0, 6x4500 10Nkg=4500000N, W Yes=GH=4500000Nx2m=9000000J T=W P=9000000J 3000w=3000S Supporting motor power p 1=p 75%=3kw

23. On average, the current intensity of a lightning bolt is about 20,000 amperes, the voltage is about 1 billion volts, and the discharge time is about seconds. Q: How many kilowatts of electrical power does an average lightning strike have? How much joules is the work done by an electric current?

24. If an electrical appliance consumes electric energy J in one hour, what is the power of the electrical appliance?

25. A lamp marked with "36V, 40W", when it is working normally, the current flowing through it is A, and the resistance at this time is If it is connected to a certain circuit, the current passing through it is 1A, and its power is W

26. How many hours can 1 kWh of electricity make a "220V, 200W" TV work normally?

You can see if these questions are okay or not.

F31 As shown in the figure, in the process of increasing the uniform speed of an object weighing 600N by 2m within 20s with a pulley block, the work done by the tensile force f is 1440J, and the useful work and mechanical efficiency of the pulley block are obtained, and the size of the tensile force f and the power of the tensile force f.

The question is how much work he does, which is the work done by Xiao Ming, because Xiao Ming has a force to give the bicycle a boarding force to make the car move, if he knows this force, he can do it, not not do no work, so it is not 0 at all, but the condition is insufficient, if he knows the friction of the ground, he can also do this problem.

If the ground friction is 40N, it is moving at a constant speed in the horizontal direction, and it receives the effect of the balance force, so the power of the car is 40N, so the power = fs t=40*100 20=200W

There is no solution to this question.

You have to know what the resistance is in order to find the power.