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The calculation of physical electric power 1. When the "220 V 40 W" and "220 V 60 W" electric lamps are connected in series in a 220 V circuit, their actual power is calculated 2. With the improvement of people's living standards, refrigerators have entered thousands of households. It is known that the rated power of a household refrigerator is 120W, and the working time of the refrigerator is not continuous. If the total working time of the refrigerator is 6h, how many kilowatt hours of electricity is consumed 3. Resistance R1 = 4 ohm, R2 = 8 ohm in series in the 24 V circuit, at this time, the electrical power of R1? 4. An electric iron needs a certain preheating time before it is used, so people often connect it to the power supply when it is not in use, which not only wastes electricity, but also causes the iron head to be oxidized and not easy to be stained with zinc. Xiao Ming connects an electric iron marked "220 V 55 W" with a bulb (the resistance of the bulb in the preheating state is 495 Ω) to form the circuit diagram as shown in the figure, The soldering iron soon reaches the welding temperature What is the power consumption of electric iron in 1 'preheating state The power consumption of the whole circuit in 2 'preheating state is several percent of that of the electric iron in normal operation ——————Electric soldering iron—— ↑ | 220V ___ Switch__ | ↓ | | | ————- light bulb————
It's simple.
1. Because according to P = u * U / R (can't square. Please forgive me)
It can be concluded that the resistance of "220 V 40 W" lamp is 1210 σ, and the other is 806.6 σ
Junior high school physics (power) calculation
The tractive force of a tractor is 2.85 * 10 ^ 4N when it ploughs, and it runs 3600m in one hour. How much work does the tractor do per hour? What is the power of the tractor?
∵F=2.85×10^4N S=3600m
∴W=FS=2.85×10^4N×3600m=1.026×10^8J
∴P=W/t=1.026×10^8J/1×3600s=2.85×10^4w
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