One degree of electricity can supply five "220 V, 40 W" electric lamps for several hours Thank you. The final answer is five hours

One degree of electricity can supply five "220 V, 40 W" electric lamps for several hours Thank you. The final answer is five hours

One kilowatt hour is 1000 watt hours
The total power of the five lamps is p = 40W × 5 = 200W
t=w/p=1000wh/200w=5h

How long does a lamp marked "220V 25W" consume 1kW · h when it works normally

1000 divided by 25 is OK. One kilowatt is one degree

How many hours can a "220 V & nbsp; 40 W" bulb work normally with 1 kW · h electric energy?

Bulb power P = 40W = 0.04kw, bulb working time t = WP = 1kW · h0.04kw = 25h

One incandescent lamp is marked with the word "220 V 100 W"
(1) Find the current of this incandescent lamp when it works normally
2) If a long wire is used to connect the incandescent lamp to a remote power supply, and the power supply voltage of the power supply is constant at 220 V, then the actual electric power of the incandescent lamp is 81 W
Note: the title does not say that the filament resistance is constant

In this case, if there is no image, it must be explained that the resistance of the filament is constant, otherwise, it cannot be calculated
It can only be calculated according to the constant resistance
1、
I=P/U＝100/220≈0.455A
Filament resistance: r = u & #178 / P = 48400 / 100 = 484 Ω
Actual power: P real = u real & R
So: u real = √ P real r = 198v
2、
Lamp current: I = 198 / 484 ≈ 0.41a
Conductor power: P loss = (220-198) × 0.41 = 9.02w