An electric lamp with a resistance of 240 ohms, designed for a voltage of 120V, must be powered

| September 26, 2021 | education

An electric lamp with a resistance of 240 ohms, designed for a voltage of 120V, must be powered from a 220V network. Determine the resistance of the conductor that must be included in the circuit in order for the lamp to work in nominal mode

Given:

R1 = 240 Ohm – resistance of the electric lamp;

U1 = 120 Volts – the voltage for which the electric lamp is designed;

U2 = 220 Volts.

It is required to determine what additional resistance R2 (Ohm) must be included in the circuit in order to ensure the operation of the lamp at a voltage of U2.

Let’s find the current for which the electric lamp is designed:

I = U1 / R1 = 120/240 = 0.5 Ampere.

Then, in order to provide such a current strength, the total resistance of the circuit should be:

R = U2 / I = 220 / 0.5 = 440 ohms.

Additional resistance will be equal to:

R2 = R – R1 = 440 – 240 = 200 ohms.

Answer: it is necessary to include a resistance equal to 200 ohms in the circuit.



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