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

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

1. Calculation the resistance of every bulb.


, for this reason


because that the 60 W bulb.

for the 100 W bulb.

2. Explain what the 60 W and 100 W ratings mean.

Answer: The bulbs room designed come be connected directly come a 120 V source. Once you run the bulbs as designed, they will certainly dissipate the rated power. If lock dissipate an ext than the rated power, lock are likely to burn out.

3. I m sorry of the complying with quantities identify the brightness the a lightbulb?

Answer: c. Power

4. Which of the complying with quantities must be the very same for each pear in a series circuit?

Answer: a. Current

5. If both lightbulbs are linked in parallel come a 120 V source, i m sorry is brighter? explain your prize briefly.

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

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

Answer: now the bulbs will each it is in dimmer than as soon as they"re linked to 120 V. However the 100 W bulb will certainly still it is in brighter. No matter what a pear is linked to, its resistance is a property of the bulb. Parallel bulbs need to take the exact same voltage. Through the equation for power , the bulb v the reduced resistance will certainly dissipate more power. The 100 W bulb has actually a smaller sized resistance, for this reason it will certainly be the brighter bulb.

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

Answer: Bulbs associated in collection each take the very same current. Power is additionally given by the equation P = I2R. With the very same current, the bulb with the bigger resistance will dissipate an ext power. Because the 60 W bulb has actually the larger resistance, it will certainly be brighter.

8. Rank the brightness the the adhering to bulbs, v 1 gift the brightest and 4 being dimmest. Justify her answer v an explanation and/or a calculation in the an are below.

Calculate the strength dissipated by every bulb.

Answer: ___60 W bulb associated to 50 V source


___100 W bulb connected to 50 V source


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

. This same existing flows with both bulbs.

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


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


Now rank follow to strength dissipated:

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

9. Describe briefly why, in your house, a 100 W pear will always be brighter 보다 a 60 W bulb.

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Answer: In a house, all electric outlets are linked in parallel to 120 V. Bulbs the you to buy in the store space rated for use on a standard household 120 V circuit. For this reason if girlfriend plug your lamps into a conventional outlet, you constantly use the bulbs at your rated voltage and also thus at their rated power. A 100 W pear at house will always dissipate an ext power 보다 a 60 W bulb and so will always be brighter.