Two lightbulbs, one rated 60 W at 120 V and also the other rated 100 W at 120 V, are arranged in two various circuits.

You are watching: The power rating on a light bulb indicates how much power it would dissipate

1. Calculate the resistance of every bulb.


, for this reason


for the 60 W bulb.

for the 100 W bulb.

2. Define what the 60 W and also 100 W ratings mean.

Answer: The bulbs space designed to be associated directly to a 120 V source. As soon as you operate the bulbs together designed, they will certainly dissipate the rated power. If lock dissipate much more than the rated power, castle are likely to burn out.

3. Which of the complying with quantities determines the brightness the a lightbulb?

Answer: c. Power

4. I beg your pardon of the adhering to quantities should be the exact same for each pear in a series circuit?

Answer: a. Current

5. If both lightbulbs are associated in parallel to a 120 V source, i m sorry is brighter? describe your price briefly.

Answer: The bulb rated at 100 W will certainly be brighter. As soon as both bulbs are associated to the rated voltage, they will certainly dissipate the rated power. The brightness the a bulb counts on the strength it dissipates, therefore the 100 W bulb will be brighter 보다 the 60 W bulb.

6. If both lightbulbs are associated in parallel come a 50 V source, which is brighter? Explain.

Answer: currently the bulbs will each be dimmer than once they"re connected to 120 V. But the 100 W bulb will still be brighter. No matter what a bulb is connected to, that is resistance is a building of the bulb. Parallel bulbs must take the exact same voltage. By the equation for power , the bulb through the reduced resistance will certainly dissipate more power. The 100 W bulb has actually a smaller resistance, for this reason it will certainly be the brighter bulb.

7. If both lightbulbs are linked in series to a 120 V source, i beg your pardon is brighter? Explain.

Answer: Bulbs linked in series each take it the very same current. Power is also given through the equation P = I2R. With the exact same current, the bulb through the bigger resistance will dissipate more power. Because the 60 W bulb has actually the larger resistance, it will be brighter.

8. Rank the brightness of the following bulbs, through 1 gift the brightest and 4 gift dimmest. Justify her answer through an explanation and/or a calculation in the space below.

Calculate the power dissipated by each bulb.

Answer: ___60 W bulb associated to 50 V source


___100 W bulb connected to 50 V source


In series: The indistinguishable resistance that the two bulbs in collection is 380W. When connected to 120 V, the current in the circuit is

. This same present flows through both bulbs.

___ 60 W pear in collection with 100 W bulb and 120 V source


___ 100 W bulb in collection with 60 W bulb and also 120 V source


Now rank according to power dissipated:

4 (10 W) 60 W bulb associated to 50 V source2 (18 W) 100 W bulb linked to 50 V source1 (25 W) 60 W bulb in collection with 100 W bulb and 120 V source3 (14 W) 100 W pear in series with 60 W bulb and 120 V source

9. Explain briefly why, in her house, a 100 W pear will always be brighter than a 60 W bulb.

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Answer: In a house, all electric outlets are connected in parallel to 120 V. Bulbs that you buy in the store space rated for use on a standard family members 120 V circuit. Therefore if girlfriend plug her lamps right into a standard outlet, you always use the bulbs at their rated voltage and also thus at their rated power. A 100 W bulb at residence will constantly dissipate more power 보다 a 60 W bulb and so will constantly be brighter.