Question

The powers of two light-bulbs are 60 W and 120 W when connected in parallel across a 110-V source. What is the power of the bulb that will output less power when the two light-bulbs are connected in series with the same source?

Answer 1

The power of the bulbs is : P1 = 26.67 W and P2 = 13.66 W

Step-by-step explanation:

Step 1: Calculate the resistance R of each light bulb

P = U*I = U²/R

R1 = U²/P1 = 110²/60 = 201.67 Ω

R2 = U²/P2 = 110²/120 = 100.83 Ω

Serial

Step 2: Calculate the current through the bulbs

I = U /( R1 + R2)

I = 110 V/ (201.67 Ω + 100.83Ω)

I = 0.3636 A

Step 3: Calculate the power of each bulb

P = U*I = I²*R

P1 = (0.3636)² * 201.67 = 26.67 W

P2 = (0.3636)² *101.83 = 13.66 W