A current of 1.5 A flows through a light bulb connected to a network with a voltage of 120 V, when an additional

| January 6, 2021 | education

A current of 1.5 A flows through a light bulb connected to a network with a voltage of 120 V, when an additional resistance was switched on in series with the light bulb, the current became equal to 1.2 A, determine the value of the additional resistance and the voltage on the light bulb when the additional resistance was switched on.

Let’s determine the resistance of the lamp using Ohm’s law.
I1 = U / R1.
R1 = U / I1 = 120 / 1.5 = 80 Ohm.
After connecting an additional resistance, the current strength became 1.2 A, then:
The total resistance of the circuit is equal to: Rob = U / I2 = 120 / 1.2 = 100 Ohm.
Then Radm = Rob – R1 = 100 – 80 = 20 Ohm.
Determine the voltage across the lamp: Ul = R1 * I2 = 80 * 1.2 = 96 V.
Answer: The additional resistance is 20 Ohm, the voltage across the lamp is 96 V.



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