There is a small bulb marked with "3V 1.5W" and resistor R1 in series in the circuit with 9V power supply. If the small bulb works normally for 1 minute, it is related to R1 in series? Chasing points There is a small bulb marked with "3V 1.5W" and resistor R1 in series in the circuit with 9V power supply. How to calculate the physical quantity related to R1 in series when the small bulb works normally for one minute?

There is a small bulb marked with "3V 1.5W" and resistor R1 in series in the circuit with 9V power supply. If the small bulb works normally for 1 minute, it is related to R1 in series? Chasing points There is a small bulb marked with "3V 1.5W" and resistor R1 in series in the circuit with 9V power supply. How to calculate the physical quantity related to R1 in series when the small bulb works normally for one minute?

When 3V 1.5W bulb works normally
I=P/U=1.5/3=0.5A
Ur=9-3=6V
RR = ur / I = 6 / 0.5 = 30 Ω
Pr=IU=0.5*6=3W
WR = PRT = 3 * 60 = 180 joules
The physical quantities related to R are as follows:
The R resistance is 30 ohm, the voltage at both ends is 6V, the current is 0.5A, the power consumed by the resistance is 3W, and the power consumed in one minute is 180J

Bulb rated voltage 3V, rated power 1.5W, resistance
Why is the result of P = u ^ 2 / r different from that of calculating rated current I first and then r = u / I? Which result should be used?

R=U^2/P=3^2/1.5=6
I=P/U=0.5
R=U/I=6
The same