After a 3V, 15W small bulb is connected in series with a 2 ohm resistor, the small bulb lights up normally Seek 1: resistance R of small bulb 2: Voltage across resistor R2 3: If the small bulb is directly connected to the power supply, the small bulb will not be burnt out

After a 3V, 15W small bulb is connected in series with a 2 ohm resistor, the small bulb lights up normally Seek 1: resistance R of small bulb 2: Voltage across resistor R2 3: If the small bulb is directly connected to the power supply, the small bulb will not be burnt out

1) According to P = UI = u ^ 2 / R, the resistance of the small bulb is r = u ^ 2 / P = 3 * 3 / 15 = 0.6 Ω 2) the current flowing through R2, I = the current when the bulb normally lights up = P / u = 15W / 3V = 5ar2, the voltage at both ends of U2 = I * R2 = 5 * 2 = 10v3) the power supply voltage, u = the voltage at both ends of the lamp + the voltage at both ends of R2 = 3 + 10 = 13V, the actual power, P = UI = u ^ 2 / r = 13 * 13 / 0.6 =

Does the "3V, 0.3A" small bulb mean that its resistance must be r = 6 / 0.3 = 20 ohm?

3V, 0.3A small bulb, resistance R = 3 / 0.3 Ω = 10 Ω
When the temperature changes, the resistance of the bulb changes, unless it is stated that this effect does not have to be taken into account