Low voltage 24 V LED lamp connected to the protection of 220 V power supply will burn out

Low voltage 24 V LED lamp connected to the protection of 220 V power supply will burn out

Yes! It's time to step down and rectify!

A 220 V, 25 W light bulb connected to 110 V power supply, ask for the power consumption
If a 110V, 8W bulb is connected to a 380V power supply, what is the resistance value of the bulb and what is the rated power of the resistance

1. If a 220 V, 25 W bulb is connected to a 110 V power supply, calculate the power consumed by it. Because r = 220 * 220 / 25, P = 110 * 110 / R, so p = 6.25 W. 2. If a 110 V, 8 W bulb is connected to a 380 V power supply, what is the value of the bulb resistance, and what is the rated power of the resistance

Incandescent lamp L1: 220 V, 100 W; L2: 220 V, 60 W
What is the actual power ratio of the two lamps?

In the following, it is assumed that the resistance of the bulb does not change with the voltage (temperature)
1. According to "r = P / u ^ 2", the ratio of resistance of two lamps is R1: R2 = 60:100 = 3:5
2. The total power of series circuit is equal to: ptotal = u ^ 2 / (R1 + R2) = u ^ 2 / (u ^ 2 / P1 + u ^ 2 / P2) = (P1 * P2) / (P1 + P2) = (100 × 60) / (100 + 60) w = 37.5W
3. According to "P = I ^ 2R", the actual power of the two lamps is proportional to the resistance when the current is the same, and the resistance of the bulb remains unchanged. The actual power of the two lamps is: P1 '= (3 / 8) × 37.5W = 14.0625w
P2'=(5/8)×37.5W=23.4375W
4. The actual power ratio of the two lamps is 3:5

Two light bulbs of 220v40w and 220v60w are connected in series on the 220V line. How much power do they actually consume

Analysis:
First, their resistances are calculated,
According to the formula r = u ^ 2 / P (from P = UI = u ^ 2 / R)
So R1: R2 = P2: P1 = 60:40 = 3:2
The current in a series circuit is equal everywhere, so
P1 real: P2 real = I1 ^ 2r1: I2 ^ 2r2 = R1: R2 = 3:2
If they are connected in series with a voltage of 220 V
Then p total = u ^ 2 / R total = 220 ^ 2 / (R1 + R2) = 220 ^ 2 / (U amount ^ 2 / P amount 1 + U amount ^ 2 / P amount 2) = P1 * P2 / (P1 + P2) = 40 * 60 / (40 + 60) = 24W
So P1 = 24 × 3 / 5 = 14.4w, P2 = 9.6w