Lightbulbs act as resistors. Janine is building a circuit that contains two lightbulbs in parallel. One of the lightbulbs has a resistance of 120 ohms, but the resistance of the second lightbulb is unknown. She models the total resistance in the circuit, t, with this equation, in which r represents the resistance of the second lightbulb.

Step-by-step explanation:

Here we need to find the total resistance of the lightbulbs connected in parallel. Giving the total resistance by the symbol t and the resistance of the second bulb by the symbol r, so here goes

Formula for resistance connected in parallel is:

Where ,

Rt denotes the total resistance

R1 denotes the resistance of 1st object

R2 denotes the resistance of the 2nd object

now since using the information from the question we deduce the formula to be :

where t gives the total resistance of both the lightbulbs connected in parallel and where r is the resistance of the second lightbulb.

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