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"Light bulbs with the wattage ratings shown in the figure above are connected in a circuit. (a) What current does the voltage source deliver to the circuit? (b) Find the power dissipated by each bulb. (Asusume normal operating resistances of the bulbs to be constant at any voltage.)"
I know P = IV = V2/R = I2R, and R = V/I. I know the current is the same for the 15W, the 40W and the combination in parallel of the 60W and 100W.
I tried expressing the power of each bulb as a ratio of the power of the first bulb, 15W:
P1 = P1, P2 = (8/3)P1, P3 = 4P1, P4 = (20/3)P1
then since the currents are equal, P1/R1 = (8/3)P2/R2
R1 = (3/8) R2
but I don't know where to go from here...especially with the parallel part. I don't know how to combine the powers in the parallel part...
"Light bulbs with the wattage ratings shown in the figure above are connected in a circuit. (a) What current does the voltage source deliver to the circuit? (b) Find the power dissipated by each bulb. (Asusume normal operating resistances of the bulbs to be constant at any voltage.)"
I know P = IV = V2/R = I2R, and R = V/I. I know the current is the same for the 15W, the 40W and the combination in parallel of the 60W and 100W.
I tried expressing the power of each bulb as a ratio of the power of the first bulb, 15W:
P1 = P1, P2 = (8/3)P1, P3 = 4P1, P4 = (20/3)P1
then since the currents are equal, P1/R1 = (8/3)P2/R2
R1 = (3/8) R2
but I don't know where to go from here...especially with the parallel part. I don't know how to combine the powers in the parallel part...
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