U = 220 V;
P = 100 W;
To solve the problem, we will use two formulas:
1) I = U / R – Ohm’s law for a section of the circuit,
2) P = I * U – power consumption of the light bulb.
We obtain a system of equations, whence P / U = U / R,
P * R = U ^ 2;
where the resistance of the filament is R = U ^ 2 / P = 220 * 220/100 = 220 * 2.2 = 484 (Ohm).
Answer: 484 ohms.
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