Two models of "220 V, 40 W" and "220 V, 60 W" incandescent lamps are connected in series in the home circuit, and their actual electric power is calculated

Two models of "220 V, 40 W" and "220 V, 60 W" incandescent lamps are connected in series in the home circuit, and their actual electric power is calculated

Resistance of 40W lamp: R1 = u & # 178 / P = 220 & # 178 / 40 = 1210 (Ω)
Resistance of 60W lamp: R2 = u & # 178 / P = 220 & # 178 / 60 = 806.7 (Ω)
Current of two lamps in series: I = u / R series = 220 / (1210 + 806.7) = 0.11A
Actual power of 40W lamp: P1 = I & # 178; R1 = 0.11 & # 178; X 1210 = 14.6 (W)
Actual power of 60W lamp: P2 = I & # 178; R2 = 0.11 & # 178; X 806.7 = 9.8 (W)

The two bulbs L1 and L2 of "220 V 40 W" are connected in series in a 220 w circuit to calculate the voltage at both ends of L1 and the total power consumed by the circuit

The rated voltage and rated power of the two bulbs are the same: u = 220 V, P = 40 W, so their resistance values are also equal, expressed by R. from P = (U) & sup2 / R: r = (U) & sup2 / P = 220 & sup2 / 40 = 1210 (Ohm), the total resistance of the circuit is: R series = R + r = 2, r = 2420 ohm

If two lamps marked with "220 V 40 W" are connected in series and connected in 220 V circuit, the total power consumed by the two lamps is 0
A.80W
B.20W
C.30W
D.40W

P=U^2/R
Each bulb u = 110
So each bulb consumes 1 / 4 of the original power
So the total power consumption of the two lamps is 20W, select B

The two lamps marked with "220 V 40 W" are connected in parallel to the home circuit, and the total power consumed by the two lamps is
If it is connected in series, the total power consumed by the two lamps is

In series, P = I * I * (2R), where R is the resistance of the lamp; in parallel, because both lamps can reach their own rated voltage, they can light normally, so p = 40 + 40 = 80W