There is a small light bulb. The resistance of the filament is 5 Ω when it lights normally, and the voltage required for normal operation is 2.5V. If we only have a 6V power supply, we need to make the small light bulb work normally______ The first resistance is______ The resistance in Ω

There is a small light bulb. The resistance of the filament is 5 Ω when it lights normally, and the voltage required for normal operation is 2.5V. If we only have a 6V power supply, we need to make the small light bulb work normally______ The first resistance is______ The resistance in Ω

According to the partial voltage characteristics of the series circuit, a resistor should be connected in series to make the small bulb shine normally on the 6V power supply. At this time, the voltage at both ends of the small bulb is 2.5V, ∵ the total voltage in the series circuit is equal to the sum of the partial voltages, ∵ the voltage at both ends of the resistor: ur = u-ul = 6v-2.5v = 3.5V, ∵ the current at all parts of the series circuit is equal, ∵ according to Ohm's law, we can get: URR = ulrl, that is, 3.5vr = 2.5 V 5 Ω, the solution is r = 7 Ω, so the answer is: string; 7

The filament of incandescent lamp is broken. If it can be used again, the resistance of filament will decrease
The filament of incandescent lamp is broken. If it can be used again, the resistance of filament will decrease. One of the reasons why the incandescent lamp used for a long time is dark is the resistance of filament（

If the filament of incandescent lamp is broken, if it can be used again, the resistance of filament will be (reduced) because one section of resistance filament is not used;
One of the reasons why incandescent lamps used for a long time are dim is that the resistance of the filament is (increased) because the resistance filament is thinner

What is the change of resistance when the filament of incandescent lamp is disconnected and connected again

The connecting part becomes thicker, the filament becomes shorter, and the cross-sectional area of the connecting part becomes larger. According to the definition of resistance, the resistance becomes smaller
The lights will be brighter, but they will burn out more easily