How much additional resistance should be taken so that a lamp that burns normally

How much additional resistance should be taken so that a lamp that burns normally at a voltage of 120 V and a current of 4 A can be connected to a 220 V network.

In order to ensure the normal combustion of the lamp under a voltage of U₁ = 120 V and with a current strength of I₁ = 4 A, it is necessary to connect an additional resistance Rd in series to it so that this circuit can be connected to a network with a voltage of U = 220 V. connection U = U₁ + U₂, while I = I₁ = I₂, where U₂ is the voltage drop and I₂ is the value of the current at the additional resistance, then:

Rd = U₂ / I₂ or Rd = (U – U₁) / I₂.

We get:

Rd = (220 V – 120 V) / 4 A; Rd = 25 Ohm.

Answer: you need to take an additional resistance equal to 25 ohms.