Then because the current of the main road is 0.5A, D+Z=0.5.
Bulb voltage
= Resistance voltage
= 30 * Z = 30 *(0.5-D)= 15-30*D
The light bulb emits light normally with rated power 108w, then
Bulb power = bulb voltage * bulb current =( 15-30*D)*D= 108.
Solve the equation: 30 * d 2- 15 * d+ 108 = 0.
have
d = 1/4+ 1/20 * I * sqrt( 14 15)， 1/4- 1/20 * I * sqrt( 14 15)
The solution is a complex number, which means that the power given by the original problem is wrong!
In addition, the 108w light bulb is definitely not a small light bulb. You can go to the store and ask, the power of ordinary fluorescent tubes is only 35w! ! ! ! !